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At  practised  by   1.  Buck  Bros.     8.  T 
Whitney  Co.     6.  J.  A.  F»y  A 

The  Miller  Bros.  Cutlery  Co.      3.  Brown  ASharpe  MTg  Co. 
7.  Hoope*  A  Townatnd.     8.  Freeland  Tool  Works.    8 

4.  Morse  Twist  Drill  C...       5.  The  Pr»tt  A 
Joshua  Oldham.      16.   R.  Hoe  A  Co. 

Patented  July  S,  1878. 


(See  Tempering  and  Hardening  Metals.) 





erjjraral  (gngmcmirg  imtr  t\t  llcrljanmtl  %xtz, 




PARK    BENJAMIN,    PH.D.,    LL.  B, 

•vox..  II. 








GEARING.  Wheel-work  in  which  motion  is  transmitted  from  one  wheel  to  another  by  means  of 
teeth  upon  their  peripheries,  is  called  gearing.  The  axes  of  a  pair  of  wheels  in  gear  may  have  dif- 
ferent relative  positions,  and  the  teeth  may  act  upon  each  other  in  different  ways.  There  are  in  con- 
sequence six  varieties  or  classes  of  gearing,  viz. :  1,  spur-gearing ;  2,  bevel-gearing ;  3,  skew-gear- 
ing ;  4,  screw-gearing  ;  5,  twisted  gearing  ;  6,  face-gearing. 

In  general,  if  the  teeth  of  wheels  in  gear  be  indefinitely  increased  in  number  and  reduced  in  size, 
they  will  ultimately  become  mere  lines,  or  elements  of  surfaces  in  contact.  These  are  called  the  pitch- 
surfaces  ;  their  relative  motions  are  the  same  as  those  of  the  wheels  from  which  they  are  thus  de- 
rived, and  their  forms  and  disposition  depend  upon  the  class  of  gearing  to  which  those  wheels  origi- 
nally belonged.  In  spur,  bevel,  and  skew  gearing,  the  surfaces  of  the  teeth  are  composed  of  right 
lines  ;  two  engaging  teeth  of  a  pair  of  either  kind  of  wheels  touch  each  other  along  a  right  line,  and 


the  teeth  are  by  the  above  process  reduced  to  rectilinear  elements  of  the  pitch-surfaces.  The  axes 
of  spur-wheels  are  parallel,  and  the  pitch-surfaces  are  cylinders ;  the  axes  of  bevel-wheels  intersect, 
and  the  pitch-surfaces  are  cones  whose  common  vertex  is  the  point  of  intersection ;  the  axes  of 
skew-wheels  lie  in  different  planes,  and  the  pitch-surfaces  are  hyperboloids.  In  all  these  cases  the 
pitch-surfaces  are  tangent  along  an  element ;  but  in  screw-gearing  the  teeth  are  of  helicoidal  form, 
and  ultimately  become  helical  elements  of  cylinders  which,  since  the  axes  are  not  in  the  same  plane, 
are  tangent  to  each  other  at  a  single  point  only.  It  is  this  fact  which  most  strikingly  marks  the  dis- 
tinction between  screw  and  twisted  gearing,  which  are  sometimes  confounded  with  each  other.  But 
in  the  latter  the  axes  are  in  the  same  plane,  and  the  teeth,  of  helicoidal  form,  finally  reduce  to  cylin- 
drical helices  or  conical  helices  upon  pitch-surfaces  which  are  tangent  along  an  element.  There  is 
no  screw-like  action  of  one  wheel  upon  the  other,  as  there  is  in  screw-gearing,  and  twisted  wheels  are 
in  fact  only  modified  forms  of  spur  or  of  bevel  wheels.  In  the  explanation  of  their  construction 


they  will  accordingly  be  treated  as  such,  although  the  peculiar  conformation  of  the  teeth  has  caused 

them  to  be  placed  in  a  distinct  class. 

These  five  varieties  are  those  most  extensively  used  in  modern  machinery,  and  the  general  appear- 
ance of  a  pair  of  wheels  and  their  pitch-surfaces,  of 
each  class,  is  shown  in  Figs.  20G4  to  2068.  Face- 
gearing  is  now  rarely  met  with ;  the  name  is  derived 
from  the  fact  that  the  wheels  were  usually  formed 
with  teeth  consisting  of  turned  pins  projecting  from 
the  faces  of  circular  disks,  as  shown  in  Fig.  2069 ;  a 
mode  of  construction  well  adapted  to  wooden  mill 


work,  and  to  that  only.  In  the  case  illustrated  here, 
these  pins,  by  indefinite  increase  in  number  and  dimi- 
nution in  size,  will  finally  become  points  in  the  cir- 
cumferences of  circles  which  roll  in  contact.  These 
axes  are  perpendicular  to  each  other,  but  turned  pins 
may  be  inserted  in  other  surfaces  than  planes,  and  in 
this  way  such  wheels  can  be  made  to  work  together 
when  the  axes  have  other  relative  positions  than  the 
one  here  shown.  All  these  may  be  properly  said  to  belong  to  the  same  class,  the  characteristics 
being  that,  whatever  the  relation  of  the  axes  or  the  general  form  of  the  wheels,  the  teeth  are  circu- 
lar in  their  transverse  sections,  touch  each  other  in  a  single  point,  and  ultimately  become  points,  the 


wheels  having  no  pitch-surfaces  properly  so  called,  although  in  constructing  them  surfaces  of  some 
kind  must  be  provided  in  which  to  secure  the  teeth. 

The  following  table  exhibits  in  a  manner  convenient  for  reference  the  peculiar  features  of  the  dif- 


ferent  kinds  of  gearing  above  mentioned.     The  teeth,  the  forms  of  whose  linear  elements  are  given 
in  the  last  column,  are  supposed  to  be  of  sensible  magnitude,  in  order  that  the  circular  sections  of 


those  in  the  last  class  may  be  kept  in  view.     For  in  face-gearing  the  increase  in  the  number  involves 
a  diminution  in  the  length  as  well  as  in  the  diameter  of  the  teeth,  so  that  at  the  limit  they  vanish 



altogether,  as  just  explained  ;  whereas  in  the  other  classes  the  length  of  the  teeth  is  not  affected  by 
any  variation  in  the  height  or  thickness,  and  they  reduce  to  lines. 


Relative  Position  of  Axes. 


Elements  of 

1.  Spur  ,        ) 

2.  Bevel....  ) 
8.  Skew . . . .  j 

4.  Screw J 

5.  Twisted.. 

6.  Face 


In  same  plane. 

Cones J- 

Hyperboloids .  J 


or                 j 


In  different  planes. 

1  Parallel 

<          In  same  plane. 

Principles  of  Forms  of  Gear-  Wheels. — The  proper  action  of  gear-wheels  of  any  kind  evidently 
depends  upon  the  forms  of  the  teeth.  In  order  to  proceed  intelligently  in  determining  these  forms, 
a  clear  understanding  of  the  principles  involved  is  necessary  ;  which  can  be  most  readily  gained  by 
first  considering  two  pieces  rotating  in  contact  about  fixed  parallel  axes. 

In  Fig.  2070,  let  C  and  D  be  the  centres  of  motion  of  the  two  curves  in  contact  at  P  ;  then,  if 
the  upper  one  turn  as  shown  by  the  arrow,  it  will  drive  the  lower  one  before  it.  Since  the  point  P  of 
the  upper  curve  moves  in  a  circle  about  D,  the  direction  of  that  motion  at  the  instant  is  perpendicu- 
lar to  D  P,  the  contact  radius,  and  its  linear  velocity  may  be  represented  by  P  E.  Through  P  draw 
T Tthe  common  tangent  of  the  curves,  and  iViV  their  common  normal:  then  Pi? may  be  resolved 
into  the  components  P  B,  P  A.  Of  these  the  former  is  ineffective,  as,  if  P  moved  in  the  direction 
of  the  tangent,  it  would  merely  slide  upon  the  lower  curve.  But  the  normal  component  PA  com- 
pels the  lower  curve  to  rotate  around  C.  The  motion  of  P  considered  as  a  point  in  this  curve  will 
therefore  be  perpendicular  to  C  P  ;  and  the  magnitude  P  F  of  this  resultant  must  be  such  that  its 
normal  component  shall  also  be  PA  :  for  if  this  component  were  greater,  the  curves  would  not  re- 
main in  contact,  and  if  less,  they  would  intersect.  Now  draw  D  H  perpendicular  to  N ' N,  thus  mak- 
ing the  triangle  D  HP  similar  to  EAP;  draw  C  G  perpendicular  to  N  N,  making  C  GP  6imilar 
to  A  PF;  also  CD  cutting  NN  in  I,  and  making  G  G  /similar  to  HD  I. 

Then,  since  angular  velocity 

Let  v  =  angular  velocity  of  upper  curve  around  D. 
"    v'=      "  "      of  lower      "  "       C. 

linear  velocity 


we  shall  have 

PE  _P  A 
P D~  WE.' 
~ PC~  CG1 




That  is  to  say,  the  angular  velocities  are  to  each  other  inversely  as  the  perpendiculars  from  the  cen- 
tres of  motion  upon  the  common  normal ;  or,  inversely  as  the  segments  into  which  the  common  nor- 
mal cuts  the  line  of  centres.  And  if  it  be  required  that  the  velocity  ratio  shall  remain  constant,  it 
follows  that  the  common  normal  must  always  cut  the  line  of  centres  in  the  same  point. 

Now,  PB  represents  the  sliding  of  the  driver,  P  0  that  of  the  follower,  upon  the  common  tan- 
gent ;  therefore  0  B,  their  difference  in  this  instance,  represents  the  sliding  of  one  piece  upon  the 
other.  Had  0  and  B  fallen  on  opposite  sides  of  NN,  this  sliding  would  have  been  P  0  +  P  B. 
But  it  is  clear  that  there  will  always  be  a  sliding  of  one  upon  the  other,  unless  the  tangential  com- 
ponents have  the  same  magnitude  "and  direction.  And  as  the  normal  component  is  the  same  for  both 
rotations,  this  can  happen  only  when  the  resultants  P  E  and  P  F  coincide  ;  in  which  case  the  contact- 
radii  DP  and  C  P,  to  which  those  resultants  are  respectively  perpendicular,  must  also  coincide  in 
one  right  line,  that  is,  in  the  line  of  centres.  In  other  words,  pure  rolling  contact  can  exist  only  when 
the  point  of  t<ui<ir,tr>i  is  on  the  line  of  centres,  as  in  Fig.  2071.  Since  P  and  J  here  fall  together,  and 
the  linear  motions  are  identical,  we  see  at  once  that  the  angular  velocities  are  inversely  as  the  contact- 
radii.  And  because,  if  the  velocity  ratio  is  to  be  also  constant,  these  contact-radii  must  remain  con- 
stant it  follows  that  the  only  curves  which  can  move  in  rolling  contact  with  a  constant  velocity  ratio  are 
two  circles,  whose  centres  arc  C  and  D,  portions  of  which  are  shown  in  dotted  lines  in  the  figure. 
These  circles  may  be  regarded  as  cut  from  the  pitch-cylinders  of  a  pair  of  spur-wheels  by  the  plane  of 
the  paper,  supposed  to  be  perpendicular  to  the  axes.  Now  the  linear  motion  of  the  point  P  in  the  driver, 
coinciding  with  the  tangent,  has  no  normal  component,  and  therefore  no  tendency  to  compel  rotation 




of  the  follower ;  which  agrees  with  the  well-known  fact  that  two  perfectly  smooth  cylinders  will 
merely  slip  upon  each  other.  Compulsory  rotation  then  requires  the  addition  of  teeth  to  circular 
wheels  ;  and  if  in  Jig.  2070  we  also  regard  the  circles  drawn  through  /  as  the  sections  of  pitch- 
cylinders,  it  will  be  clear  that  the  contact-curves  shown  in  that  figure  will  fulfill  the  functions  of 
teeth  if  they  be  of  such  form  that  their  common  normal  shall  always  pass  through  J. 

The  principle  upon  which  the  finding  of  such  curves  depends  is  illustrated  in  Fig.  2072.  A  piece 
with  a  curved  edge,  P  B  D,  is  fixed  upon  a  plane  surface ;  and  HA  C  is  a  loose  curved  ruler  which 
may  roll  upon  it.  The  two  curves  are  now  in  contact  at  P :  let  the  upper  one  roll  to  the  right  as 
shown  by  the  arrow ;  which  means  that  each  point  in  its  order  of  the  one  shall  come  into  contact 
with  each  point  in  its  order  of  the  other.  Thus,  PA  is  equal  to  P B,  and  A  will  come  into  contact 
with  B  ;  PACis  equal  to  P  B  D,  and  C  will  come  into  contact  with  D.  At  the  present  instant  P 
is  the  centre  upon  which  the  upper  curve  is  turning.  Every  point  in  it  or  rigidly  connected  with  it  is 
therefore  moving  in  a  circular  arc  of  which  P  is  the  centre.  Thus  the  motion  of  C  is  at  the  instant 
in  the  direction  C  E,  tangent  to  that  arc,  or  perpendicular  to  C  P.  C  E  is  therefore  tangent  to  the 
curve  C  D,  which  will  be  traced  on  the  plane  to  which  P  B  D  is  fastened,  and  CPis  normal  to  it. 
The  point  C  is  on  the  rolling  curve  ;  but  this  is  not  necessary.  A  marking-point,  for  instance,  may 
be  placed  at  L  ;  and  it  is  at  the  instant  moving  in  the  direction  L  O,  perpendicular  to  LP,  and  L  O 
would  be  tangent  to  the  curve  traced  by  L  upon  the  plane.  At  the  next  instant  the  point  of  contact 
will  change,  but  that  point  is  always  the  centre  about  which  the  rolling  curve  is  turning.  Thus  when 
A  reaches  the  fixed  curve  at  the  point  B,  the  latter  will  be  the  instantaneous  axis.  It  is  not  neces- 
sary that  PB D  should  be  fixed  :  we  may  suppose  the  upper  curve  to  be  fixed,  and  the  lower  one  to 
roll  upon  it,  carrying  the  attached  plane  under  the  tracing-point  C  ;  or  both  may  be  in  actual  motion, 
provided  that  the  relative  motions  are  such  that  the  one  measures  itself  off  upon  the  other.  The 
principle  is  that,  if  one  curve  move  in  rolling  contact  with  another,  the  point  of  contact  is  the  in- 
stantaneous axis,  through  which  passes  the  normal  to  any  line  traced  by  a  point  connected  with  one 
upon  the  plane  of  the  other. 



The  application  of  the  above  principles  to  the  construction  of  the  teeth  of  spur-wheels  is  shown 
in  Fig.  2073.  Let  CD  be  the  axes,  perpendicular  to  the  paper,  and  L P B,  O  P  G,  parts  of  the 
pitch-circles,  or  sections  of  the  pitch-cylinders,  in  contact  at  P.  Let  E  be  the  centre  of  another 
circle  tangent  also  at  P  to  the  other  two,  and  carrying  at  Pa  marking-point.  Let  these  three 
circles  roll  in  contact  as  shown  by  the  arrows,  with  the  same  linear  velocity.  Then,  while  the 
lower  pitch-circle  turns  through  the  angle  P D  G,  the  upper  one  will  turn  through  the  angle  PCS, 
and  the  describing  circle  through  the  angle  P  E A,  the  arcs  P  G,  P B,  and  PA  being  equal ;  and 
meantime  the  marking-point  will  have  traced  the  curves  G  A,  B  A  on  the  planes  of  the  lower  and 
upper  pitch-circles  respectively.  Evidently,  A  G  is  the  epicycloid  formed  by  rolling  the  describing 
circle  on  the  outside  of  the  lower  pitch-circle,  and  A  B  is  the  hypocycloid  generated  by  rolling  the 
same  describing  circle  on  the  inside  of  the  upper  pitch-circle.  And  from  what  precedes  it  is  clear 
that  these  curves  will  act  together  properly  as  parts  of  the  outlines  of  teeth.  P  J,  P I  represent 
the  same  curves  in  contact  at  P ;  and  the  wheel  D  being  turned  to  the  right,  Ps/will  drive  PI  be- 
fore it,  the  point  of  contact  being  on  the  arc  P  A,  the  common  normal  passing  always  through  Py 
and  the  velocity  ratio  being  constant,  until  J  and  /  come  together  at  A.  Ilere  the  action  ends,  and, 
the  rotation  being  kept  up  by  other  teeth,  this  pair  of  curves  quit  contact.  While  it  is  not  necessary 
that  a  circle  should  be  taken  as  the  describing  curve,  it  is  more  convenient  in  practice ;  and  the  teeth 
whose  forms  are  thus  determined,  known  as  epicydoidal,  are  those  most  extensively  employed.  The 
curve  A  G,  which  lies  without  the  pitch-circle  of  its  wheel,  is  technically  called  the  face  of  the 
tooth ;  and  the  curve  A  B,  lying  within  the  pitch-circle,  is  called  the  flank  of  the  tooth  to  which  it 
belongs.  Usually  the  teeth  of  each  wheel  have  both  faces  and  flanks ;  but  as  continuous  rotation 
can  be  and  sometimes  is  kept  up  without  the  aid  of  other  curves  than  those  shown,  we  will  first  con- 
sider the  conditions  under  which  this  is  possible. 

The  arc  of  the  pitch-circle  occupied  by  a  tooth  and  a  space  is  called  the  pitch  of  the  teeth  ;  and  a 
fractional  tooth  being  impossible,  the  pitch  must  be  an  aliquot  part  of  the  circumference.  If  two 
wheels  gear  together,  the  pitch  must  be  the  same  in  each,  so  that  the  numbers  of  the  teeth  must 
have  the  same  ratio  as  the  diameters  of  the  pitch-circles.  The  problem  usually  presented  in  practice 
is,  to  construct  a  pair  of  wheels  which  shall  work  with  a  given  velocity  ratio  upon  axes  also  given  in 
position.  The  distance  between  the  centres,  being  thus  known,  is  divided  into  segments  having  the 
given  ratio,  and  the  pitch-circles,  described  with  these  segments  as  radii,  are  divided  into  as  many 
equal  parts  as  it  is  proposed  to  have  teeth.  The  pitch,  being  thus  found,  is  again  divided  into  two 
parts,  one  being  the  thickness  of  the  tooth,  the  other  the  breadth  of  a  space.  If  absolutely  accurate 
workmanship  were  possible,  these  parts  might  be  exactly  equal ;  but  as  it  is  not,  the  space  must  in 
practice  be  a  little  greater.  The  difference  is  called  backlash :  if  the  wheels  are  to  be  cast  merely,  it 
is  customary  to  make  this  a  certain  fraction  (from  fa  to  fa)  of  the  pitch  ;  but  in  cut  gearing  of  any 
pretensions  to  accuracy,  there  is  no  reason  why  it  should  be  anything  like  so  large,  or  why  it  should 
vary  with  the  pitch  ;  it  should  be  as  small  as  the  skill  of  the  workman  can  make  it  with  the  tools  at 

Now,  referring  again  to  Fig.  2073,  let  us  suppose  that  P  G  had  been  determined  as  the  pitch,  and 
G  H  as  the  thickness  of  a  tooth,  on  the  wheel  D.  Having  selected  a  describing  circle  and  construct- 
ed the  curve  G  A,  the  tooth  is  then  to  be  completed  by  drawing  the  similar  but  reversed  curve  HA. 
This  diagram  is  so  proportioned  that  these  curves  intersect  at  A,  and  we  see  that  this  is  the  limiting 
case ;  the  angle  of  action  P  D  G  is  equal  to  the  pitch,  and  it  cannot  be  made  less,  or  one  tooth  would 
cease  to  act  before  the  next  one  began.  This  determines  the  necessary  length  of  the  face  AG;  and 
since  the  opposite  face  also  passes  through  A,  it  is  just  possible  to  make  the  tooth,  which  in  this  case 
is  pointed,  of  the  requisite  length.  In  this  case  also  the  line  A  D  bisects  G  H,  and  is  the  radius  of 
symmetry.  But  if,  after  determining  A,  the  arc  G  H  had  been  so  cut  by  A  D  that  G  F  were  less 
than  Elf,  the  tooth  might  have  been  made  longer  by  continuing  both  faces,  thus  increasing  the  angle 
of  action,  or  it  would  be  of  some  thickness  at  the  top,  as  in  the  next  figure  ;  but  if  G  E  had  been 
greater  than  E H,  the  construction  would  have  been  impossible,  the  two  faces  intersecting  below  the 
point  A.  Now  it  is  clear  that  a  limiting  case  like  this  cannot  be  safely  adopted  in  practice ;  the  least 
inaccuracy  in  workmanship,  or  a  very  little  wear  (to  which  pointed  teeth  of  this  form  are  especially 
liable),  will  reduce  the  angle  of  action,  and  cause  one  tooth  to  quit  correct  driving  contact  before  the 
next  one  begins  to  act.  We  say  correct  driving  contact :  if  in  Fig.  2073  we  remove  the  second  tooth 
P  J K,  the  face  A  G  of  the  first  one  will  push  the  flank  A  B  out  of  its  way,  and  so  turn  the  upper 
wheel ;  but  the  acting  curves  will  not  be  tangent  to  each  other,  nor  will  the  velocity  ratio  be  constant, 
but  the  speed  of  C  will  diminish.  Each  tooth  should  therefore  come  into  action  before  the  preced- 
ing one  goes  out ;  that  is,  the  arc  of  action  P  G  should  be  greater  than  the  pitch,  as  in  Fig.  2074, 
which  illustrates  a  case  practically  feasible. 

The  construction  is  as  follows:  Having  set  off  from  P  the  equal  arcs  of  action  P  G,  P B,  greater 
than  the  pitch,  and  selected  the  describing  circle,  we  construct  the  epicycloidal  face  G  A  and  the 
hypocycloidal  flank  B  A.  Drawing  A  D,  it  cuts  the  lower  pitch-circle  in  E,  and  we  find  G  E  to  be 
less  than  half  the  thickness  of  the  tooth  G  H,  so  that,  drawing  the  reversed  face  through  H,  the 
tooth  is  not  pointed,  but  "topped  off"  by  the  circle  V  A  W.  The  pitch-circles  having  been  pre- 
viously divided,  starting  at  the  points  G,  B,  the  other  teeth  of  the  lower  wheel  are  drawn  in  their 
proper  positions,  the  spaces  between  them  being  bounded  cot  by  the  pitch-circle,  but  by  a  circle  a 
little  inside  of  it,  giving  a  little  clearance  for  the  tops  of  the  teeth  on  the  upper  wheel,  the  faces 
A  G,  etc.,  being  continued  within  the  pitch-circle  by  tangent  radii.  Now,  as  to  the  tooth  of  the 
upper  wheel,  B  A  is  the  whole  of  the  acting  flank ;  but  the  space  must  clearly  be  made  considerably 
deeper,  to  allow  the  passage  of  the  tooth  of  the  lower  wheel.  The  exact  form  of  this  space  is  im- 
material, so  long  as  the  space  is  great  enough ;  but  it  is  usual  to  extend  the  hypocycloid  B  A  to  S  as 
shown,  the  bottoms  of  the  spaces  being  formed  by  a  circle  whose  centre  is  C,  which  allows  also  a 


clearance  between  it  and  the  tops  of  the  engaging  teeth.  When  it  is  possible  to  construct  wheels  in 
this  way,  they  will  fulfill  perfectly  the  requirement  of  transmitting  continuous  rotation  with  a  con- 
stant velocity  ratio.  But  if  the  wheel  C,  for  example,  be  very  small  in  proportion  to  D,  the  teeth 
of  the  latter  will  require  to  be  very  long,  and  in  many  if  not  most  cases  this  construction  will  be 
impossible  ;  and  in  many  cases  it  is  not  desirable  even  when  possible,  for  a  reason  which  will  appear 
from  the  following  considerations :  If  we  suppose  D  to  be  the  driver,  and  to  turn  to  the  right,  the 
action  begins  at  P  and  ends  at  A,  the  point  of  contact  continually  receding  from  the  line  of  centres. 
But  if  we  suppose  C  to  drive  in  the  opposite  direction,  the  action  begins  at  A  and  ends  at  P,  and 
the  point  of  contact  is  continually  approaching  the  line  of  centres.  There  is  during  the  action  an 
amount  of  sliding  equal  to  the  difference  between  the  lengths  of  the  acting  curves  A  G,  A  B  ;  and 
it  has  been  found  that  the  friction  is  greater  and  more  injurious  in  the  latter  case  than  in  the  former, 
the  difference  being  analogous  to  that  between  pushing  and  drawing  a  cane  over  a  pavement  to  which 
it  is  inclined.  Of  such  a  pair  of  wheels,  then,  the  one  whose  teeth  have  faces  ought  always  to  drive, 
and  the  one  with  flanks  only  ought  always  to  be  the  follower.  But  in  many  cases  a  wheel  must  be 
turned  by  another,  and  also  drive  a  third.  And  besides,  it  is  to  be  noted  that  the  longer  the  face 
of  the  tooth,  the  greater  is  the  angle  between  the  line  of  action  PA,  Fig.  2073,  and  the  common 
tangent  of  the  pitch-circles  P  T.  The  pressure  as  well  as  the  motion  acts  in  this  line  ;  and  the  great- 
er this  obliquity,  the  greater  will  be  the  component  in  the  line  CD,  that  is,  the  greater  will  be  the 

pressure  on  the  journals.  And  finally,  the  difference  between  the  lengths  of  the  face  and  the  flank 
which  act  together,  and  therefore  the  sliding,  increases  more  and  more  rapidly  as  we  recede  from  the 
pitch-circles.  This  latter  fact  is  sufficient  to  show  that  the  teeth  of  wheels  ought  always  to  be  as 
small  and  numerous  as  possible  ;  though  this  is  in  many  cases  also  affected  by  considerations  relating 
to  the  pressure  to  be  transmitted  and  the  strength  of  the  materials  to  be  used,  with  which  we  have 
nothing  to  do. 

It  will  now  readily  be  seen,  that  by  using  another  describing  circle  on  the  other  side  of  the  point 
P,  as  in  Fig.  2075,  thus  giving  both  "faces  and  flanks  to  the  teeth  of  each  wheel,  two  things  will  be 
accomplished :  a  given  angle  of  action  may  be  secured  with  shorter  faces  and  therefore  less  sliding, 
and  this  angle  will  be  divided  into  an  angle  of  approaching  and  an  angle  of  receding  action,  thus 
enabling  us  to  use  either  wheel  as  the  driver.  If  a  wheel  has  both  to  drive  and  to  follow,  it  may  be 
well  to  subdivide  the  angle  of  action  equally ;  but  in  case  it  is  to  act  as  a  driver  only,  its  arc  of 
approach  may  advantageously  be  made  less  than  its  arc  of  recess,  in  order  to  reduce  the  amount  of 
the  more  injurious  friction.  The  diameters  of  the  pitch-circles  and  the  numbers  of  the  teeth  being 
given,  the  pitch  is  determined,  and,  making  the  allowance  for  backlash,  we  find  the  thickness  of  the 
tooth.  If  we  then  assume  the  arcs  of  approach  and  of  recess,  we  can  determine  whether  the  pro- 
posed conditions  can  be  satisfied,  and  if  so,  the  forms  of  the  teeth  as  well  as  their  heights,  by  con- 
structing the  diagram,  Fig.  2075,  thus:  Let  D  be  the  driver,  and  P  0  its  arc  of  approach,  which  is 


equal  to  PL,  that  of  the  follower.  Taking  any  point  Z  on  D  P  as  the  centre  of  a  describing  circle, 
draw  the  epicycloid  L  R  by  rolling  it  on  the  outside  of  L  P  B,  and  the  hypocycloid  0  R  by  roiling  it 
within  0  P  G.  These  curves  are  respectively  the  face  of  the  follower's  tooth  and  the  flank  of  the 
driver's.  Draw  the  radius  P  C,  cutting  the  pitch-circle  of  the  follower  in  S :  if  L  iS  be  just  half  the 
thickness  of  the  tooth,  the  construction  is  so  far  possible,  but  the  follower's  teeth  will  be  pointed ; 
if  L  S  be  less  than  that,  the  teeth  will  be  "  topped  off,"  but  if  greater,  the  size  of  the  describing  circle 
must  be  increased  or  the  arc  of  approach  diminished.  The  construction  of  the  remainder  is  precise- 
ly like  that  of  Fig.  2073,  above  explained.  We  have  here  assumed  possible  conditions,  and  the 
action  is  readily  traced.     The  arrows  indicating  the  direction  of  the  rotations,  the  driver's  flank 


begins  to  act  upon  the  face  of  the  follower  at  R,  and  acts  upon  it  until  0  and  L  come  together  at  P, 
the  point  of  contact  lying  always  in  the  arc  R  P.  These  two  curves  now  quit  contact,  and  the  action 
is  continued  between  the  face  of  the  driver's  tooth  and  the  flank  of  the  follower's,  ending  at  A,  as 
in  Fig.  2073.  The  teeth  are  completed  by  extending  the  flanks,  as  in  Fig.  2074,  to  form  the  clearing 
spaces,  and  will  present  the  appearance  shown  in  Fig.  2076. 

Nothing  has  been  said  thus  far  about  the  diameter  of  the  describing  circle.  In  Fig.  2077  are 
shown  three  cases,  this  diameter  being  equal  to,  less,  and  greater  than  the  radius  of  the  pitch-circle 
within  which  the  describing  circle  rolls.  In  the  first  case  the  hypocycloid  B  A  becomes  a  diameter 
of  the  pitch-circle,  and  the  tooth,  having  radial  flanks,  is  weak  at  the  root.  In  the  second  case  the 
flank  is  tangent  to  the  radius  B  C  at  B,  and  curves  away  from  it  as  it  recedes  from  the  pitch-circle, 
giving  a  much  stronger  form  of  tooth,  which  is  therefore  to  be  preferred  for  heavy  work.  In  the 
third  case  the  flank  is  still  tangent  to  the  radius  B  C  at  B,  but  curves  in  the  opposite  direction,  the 
tooth  consequently  being  not  only  weak  but  difficult  to  make.  But  with  a  given  arc  of  action  the 
greatest  obliquity  of  the  normal  will  be  less,  the  greater  the  diameter  of  the  describing  circle;  so 
that  in  watchwork  or  other  delicate  mechanism  the  third  form  might  be  employed. 

It  will  be  noted  that  the  face  and  the  flank,  which  act  in  contact,  are  generated  by  the  same  describ- 
ing circle.  Consequently,  if  it  be  required  to  make  a  set  of  wheels  such  that  any  two  of  them  shall 
gear  correctly  together,  not  only  must  the  pitch  be  the  same  in  all,  but  the  same  describing  circle 
must  be  used  for  tracing  all  the  faces  and  all  the  flanks.  And  the  diameter  of  this,  for  the  reason 
just  pointed  out,  should  not  be  greater  than  the  radius  of  the  smallest  wheel  of  the  set.     If  it  be 


just  equal  to  that  radius,  that  wheel  will  have  teeth  with  radial  flanks ;  but  these  may  be  materially 
strengthened  by  joining  them  to  the  bottoms  of  the  clearing  spaces  by  circular  arcs,  as  in  Fig.  2079  ; 
which  indeed  can  be  done  in  any  case,  as  the  depth  of  the  space  is  considerably  greater  than  the 
length  of  the  acting  flank,  as  shown  in  Fig.  2074. 


From  Fig.  2075  it  appears  that  the  arc  of  approach  varies  with  the  length  of  the  face  of  the  fol. 
lower,  the  arc  of  recess  with  that  of  the  face  of  the  driver.  If  it  be  imperative,  then,  that  the  lat- 
ter arc  be  the  greater,  the  length  of  the  face  of  a  tooth  will  depend  upon  whether  it  is  to  drive  or 
be  driven.  But  in  the  majority  of  cases  in  ordinary  practice  this  is  not  essential ;  and  among  mill- 
wrights the  custom  obtains  of  disregarding  this  distinction,  and  making  the  depth  of  the  tooth, 
within  and  beyond  the  pitch-line,  bear  certain  definite  proportions  to  the  pitch  itself.  In  Fig.  2078 
are  shown  three  slightly  different  proportions.  In  the  first  the  whole  depth  is  two-thirds  of  the 
pitch,  the  part  within  being  to  that  without  the  pitch-circle  as  5  to  4  ;  in  the  second  the  whole  depth  is 
four-fifths  of  the  pitch,  divided  in  the  proportion  of  13  to  11 ;  and  in  the  third  we  have  four-tenths 
within  and  three-tenths  without  the  pitch-circle.  By  adopting  either  of  these  systems  of  propor- 
tioning the  teeth,  the  wheels  will  work  together  without  ii.-k  of  a  tooth  going  out  of  gear  too  soon, 
provided  that  none  of  them  have  less  than  15  teeth  ;  but  of  course  the  arcs  of  approach  and  of 
recess  will  vary  according  to  the  numbers  of  the  teeth  and  the  size  of  the  describing  circles  se- 
lected. But  as  the  locus  of  contact  is  always  the  circumference  of  that  describing  circle,  it  is  easy 
to  determine  by  the  diagram,  Fig.  2075,  what  these  arcs  are.  And  as  the  necessary  arc  of  action, 
and  with  it  the  necessary  length  of  the  face,  increases  with  the  pitch,  it  will  be  found  that  these 
proportions,  though  pood  within  the  limits  named,  will  not  answer  if  the  number  of  teeth  in  a  wheel 
be  small ;  and  the  length  of  the  tooth  must  be  determined  in  such  cases  by  actual  construction,  as 
above  explained. 

Back  and  Wheel. — If  one  of  a  pair  of  wheels  become  infinitely  large,  its  pitch-circle  will  become 
a  right  line  tangent  to  that  of  the  other  wheel,  as  O  G,  Fig.  207V.  The  similarity  of  this  diagram 
to  Fig.  2075  is  BO  great,  that  hardly  any  explanation  is  needed.  The  same  or  different  describing 
circles,  on  opposite  Bides  of  the  point  of  contact,  are  used  for  generating  the  acting  curves,  the  teeth 
of  the  wheel  having  epicycloidal  faces  and  hypocycloidal  flanks  as  before,  while  both  faces  and  flanks 
of  the  rack-teeth  are  cycloids.  The  arc  of  action  L  P  B  of  the  wheel  is  of  course  equal  to  O  P  <•' 
on  the  pitch-line  of  the  rack,  /.  P  being  equal  to  0  P,  and  P  B  equal  to  P  O,  and  the  necessary 
lengths  of  the  faces  and  flanks  are  determined,  the  teeth  completed,  and  the  clearing  spaces  formed 
exactly  as  in  Fig.  2075  ;  the  only  point  of  difference  being,  that  when  the  pitch  and  the  arc  of 
action  are  assumed,  and  the  necessary  length  of  the  cycloidal  face  A  0  of  the  rack-tooth  has  been 
found,  the  possibility  of  satisfying  tlie  conditions  is  determined  by  drawing  a  perpendicular  to  O  G 
from  A,  cutting  the  pitch-line  in  F:  if  F  G  be  less  than  or  equal  to  half  the  thickness  of  a  tooth, 
the  construction  is  possible;  but  if  greater,  it  is  not.  If  the  describing  circles  F,  Z  be  of  equal 
diameters,  and  the  same  circle  be  used  for  the  faces  and  flanks  of  a  set  of  wheels,  any  one  of  them 
will  gear  correctly  with  the  rack  if  the  pitch  be  the  same. 

If,  as  in  Fig.  2080,  the  upper  describing  circle  be  of  half  the  diameter  of  the  pitch-circle,  the 
flanks  of  the  wheel-teeth  become  radial.  We  may  assume  a  similar  case  below  ;  but  the  pitch-circle 
of  the  rack  being  of  infinite  diameter,  its  radius  is  also  infinite,  and  the  describing  circle  is  there- 
fore the  pitch-line  of  the  rack,  which  rolling  on  the  upper  pitch-circle  gives  involutes  of  that  circle 
for  the  faces  of  the  wheel-teeth.  Thus,  let  L  P,  the  arc  of  approach,  be  equal  to  O  P  on  the  pitch- 
line  ;  then,  as  the  rotation  progresses,  a  marking-point  at  O  will  trace  on  the  plane  of  the  wheel  the 
involute  O  L,  and  on  the  plane  of  the  rack  the  traced  curve  will  degenerate  into  the  point  O,  which 
will  meet  L  at  /'.  The  action  is  therefore  bad,  the  wear  during  approach  being  confined  to  this 
single  point  on  the  rack-tooth,  which  has  no  flank  proper.  A  clearing  space  is  however  needed,  and 
O  V  may  be  a  circular  arc  whose  centre  is  P  and  radius  P  O,  the  radius  of  curvature  of  the  invo- 
lute O  L  at  O. 

Annular  Wheels. — An  annular  or  internally-toothed  wheel  may  either  drive  or  be  driven.  The 
construction  of  the  teeth  in  the  former  case  is  illustrated  in  Fig.  2081.  The  diameter  of  the  describ- 
ing circle  E  is,  for  reasons  before  explained,  taken  less  than  the  radius  of  the  smaller  wheel :  both 
the  face  J.  67  of  the  driver's  tooth  and  the  flank  A  B  of  the  follower's  lie  within  the  pitch-circle  and 
are  hypocycloidal.  Since  the  pitch-circles  both  curve  in  the  same  direction,  the  teeth  continue  longer 
in  gear  than  in  the  case  of  external  contact,  and  it  is  usually  unnecessary  to  have  any  arc  of 
approach ;  but  should  it  be  required,  it  may  be  obtained  thus :  Let  P  O  be  equal  to  PL;  then  a 
tracing-point  fixed  at  O  in  the  outer  pitch-circle  will  mark  on  the  plane  of  the  inner  one  the  internal 
epicycloid  O  L,  and  on  its  own  plane  merely  the  point  O,  to  which  therefore  the  action  of  the  fol- 
lower's face  is  confined.  The  possibility  of  "satisfying  the  assumed  conditions  is  determined  exactly 
as  in  the  cases  already  described.  Thus,  A  G  is  the  necessary  length  of  the  driver's  face,  with  the 
given  describing  circle  and  for  the  arc  of  recess  P  G.  Draw  D  A  cutting  the  pitch  circle  in  F; 
then  F  G  must  not  be  greater  than  half  the  thickness  of  the  tooth,  which  is  known  if  the  number 
of  teeth  be  assigned.  The  clearing  space  of  the  follower  is  formed  as  usual  by  continuing  the 
hypocycloidal  flank  to  the  requisite  depth  ;  in  the  annular  wheel  a  short  radial  line,  tangent  to  the 
face  A  G  at  G,  is  drawn  to  limit  this  space  on  the  side,  the  bottom  being  a  circle  whose  centre  is 
D.  In  both  wheels  the  corners  of  the  spaces  may  be  rounded.  Now  it  will  be  seen  that  if  the 
pinion  drive,  the  action  will  be  confined  to  the  arc  of  recess  by  cutting  down  the  faces  of  the  teeth 
of  the  wheel  to  the  pitch-line;  and  by  reducing  their  length  to  a  less  extent,  and  increasing  the  face 
of  the  pinion's  tooth,  the  action  may  be  divided  in  any  desired  proportion.  In  all  cases,  however, 
it  is  better  to  have  no  arc  of  approach  if  it  can  be  avoided  without  unduly  lengthening  the  face  of 
the  driving  tooth,  which  increases  the  obliquity  of  the  line  of  action  and  also  the  sliding.  But  we 
have  also  just  seen  that  the  action  of  the  curve  O  L  is  confined  to  the  single  point  O  on  the  outer 
wheel ;  and  this  is  a  serious  objection  to  the  method  above  mentioned  of  forming  the  teeth  when  the 
pinion  is  to  drive. 

A  much  better  way  is  shown  in  Fig.  2082,  a  describing  circle  E  being  used  whose  diameter  is  equal 
to  or  greater  than  the  radius  of  the  annular  wheel,  and  always  greater  than  the  diameter  of  the  pin- 
ion.    The  hypocycloidal  face  of  the  wheel-tooth  will  therefore  either  be  a  radius,  or,  as  in  the  figure, 


a  Hue  curving  away  from  the  radius  D  G  ;  and  the  pinion-tooth  is  also  a  face  instead  of  a  flank,  as 
it  lies  without  its  pitch-circle.  The  sides  of  the  clearing  spaces  in  the  wheel  and  the  pinion  may  be 
any  circular  arcs  tangent  to  the  radii  at  their  extremities,  and  of  less  curvature  than  the  faces  A  Bt 
A  G  respectively.     It  will  be  noted  that  in  this  construction  it  will  in  many  cases  be  possible,  as  in 

the  figure,  by  taking  the  describing  circle  of  proper  diameter,  to  make  the  acting  faces  A  B,  A  G  of 
very  nearly  equal  length.  When  this  can  be  done,  it  is  an  advantage,  as  the  wear  of  the  two  sur- 
faces will  then  be  the  same. 

In  laying  out  annular  gearing,  when  the  internal  wheel  is  large,  care  must  be  taken  that  the  teeth 
are  not  too  long  to  clear  each  other  ;  which  may  require  attention  to  the  following  consideration :  If 



in  Fig.  2082  we  roll  the  pinion  round  within  the  wheel,  the  point  A  of  the  pinion-tooth  will  trace  an 
epitrochoid  on  the  plane  of  the  outer  wheel,  which  may  be  readily  constructed,  and  obviously  must 
clear  the  points  of  the  teeth  of  the  annular  wheel.  Similarly  the  highest  point  of  the  tooth  of  that 
wheel,  in  rolling  round  the  pinion,  will  trace  on  the  plane  of  the  latter  an  epitrochoid,  which  must 
clear  the  points  of  the  teeth  of  the  pinion. 

Pin-  Wheels  or  Trundles. — A  modification  of  epicycloidal  gearing  is  shown  in  Fig.  2083.  Let  a 
marking-point  be  fixed  at  P  in  the  upper  pitch-circle  ;  then  it  will  trace  upon  the  plane  of  the  lower 
one,  while  the  latter  turns  through  the  angle  PI)  B,  the  curve  £  A,  the  ares  P  £,  PA  being  equal. 
This  curve  is  simply  the  epicycloid  generated  by  rolling  the  upper  pitch-circle  on  the  lower ;  the  curve 
traced  on  the  plane  of  the  upper  degenerates  into  a  point.  P  F  is  a  curve  similar  and  equal  to  £  A  ; 
and  if  we  suppose  Pto  be  a  pin  of  no  sensible  diameter,  fixed  in  the  wheel  (',  this  curve  will  drive 
the  pin  as  shown  by  the  arrow,  the  action  ending  at  A.  Now  if  Pi?  be  the  pitch,  we  can  construct 
the  elementary  tooth  by  drawing  the  reverse  faces  £  A  E,  P  G  E,  which  will  drive  the  pins  in  either 
direction.  These  faces  intersect  in  A',  thus  limiting  the  height  of  the  tooth  when  the  pitch  is  as- 
sumed. In  the  diagram  E  falls  within  the  pitch-circle  of  the  upper  wheel,  and  the  face  of  the  tooth 
may  be  made  longer  than  £  A,  thus  making  the  arc  of  action  greater  than  the  pitch  :  had  E  fallen 
on  the  circumference  of  C,  we  should  have  had  the  limiting  case,  the  action  on  one  pin  continuing 
barely  long  enough  lor  that  on  the  next  to  begin. 

Practically,  the  pins  must  have  a  sensible  diameter,  and  are  made  cylindrical,  being  technically 
called  stavi .-,  which  arc  usually  inserted  into  two  circular  disks  fixed  on  the  axis,  thus  forming  what 
in  mill-work  is  called  a  trundle  or  lantern.  The  form  of  the  tooth  of  the  wheel  is  derived  from  the 
epicycloid,  by  drawing  a  curve  at  a  constant  normal  distance  from  it  ;  which  is  done  graphically  by 
describing  any  number  of  circular  arcs  with  a  radius  equal  to  that  of  the  pin,  the  centres  being  on 
the  epicycloid,  and  making  the  new  curve  tangent  to  them  all,  as  in  Fig.  2084. 

When  the  number  of  teeth,  or  in  other  words  the  pitch,  is  assigned,  it  is  necessary  to  ascertain 
what  diameter  can  be  given  to  the  pins.  This  is  done  as  in  Fig.  2086,  thus:  Lit  J' IS  be  the  pitch 
on  the  driver  />,  I'  A  that  on  the  follower  C  ;  draw  PA,  bisect  PB  in  &t  and  draw  1)  G,  producing 
it  to  cut  J'  A  in  //.-  then  the  pin  may  have  any  radius  less  than  A  //.  For,  drawing  the  elementary 
tooth  P E £,  we  see  that  PA  is  normal  to  the  epicycloid  BA  E,  to  the  parallel  or  derived  curve, 
and  to  the  circumference  of  the  pin.  If  we  assume  A  II  as  the  radius  of  the  latter,  it  is  plain  that 
the  highest  point  of  the  tooth  will  be  //,  and  that  it  will  be  just  quitting  contact  when  the  next  one 
comes  into  action.  "With  the  smaller  radius  used  in  the  figure,  the  derived  tooth-outlines  would  inter- 
sect at  1  on  the  radius  D  E,  and  the  tooth,  if  it  were  desirable  to  have  it  pointed,  might  be  extended 
to  that  point.  It  is  however  better  to  have  it  "topped  off"  as  shown,  which  may  now  safely  be 
done,  as  the  action  on  A  is  not  yet  ended,  while  the  next  tooth  has  begun  to  drive  the  pin  P.  In 
the  elementary  form,  Fig.  2083,  it  is  seen  that  the  action  is  wholly  confined  to  the  are  of  recess,  if 
the  teeth  are  given  to  the  driver.  When  the  pins  are  of  sensible  diameter,  as  in  Fig.  2085,  there  is 
an  arc  of  approach,  but  a  comparatively  small  one  ;  so  that  in  practice  the  pins  are  invariably  given 
to  the  follower. 

In  the  ca-e  of  the  rack,  then,  the  form  is  materially  different  if  it  drive  from  that  which  it  has  if 
driven.  Fig.  2086  shows  the  construction  in  the  former  case;  the  elementary  rack-tooth  being  the 
cycloid  traced  by  the  pitch-circle  of  the  wheel  rolling  on  its  tangent,  from  which  the  practical  tooth- 
outline  is  derived  as  before.  In  determining  the  radius  of  the  pin,  the  line  corresponding  to  the 
radius  J)  G  of  Fig.  2085  here  becomes  perpendicular  to  the  pitch-line  of  the  rack.  If  the  wheel 
drive,  the  pins  arc  given  to  the  rack,  and  the  elementary  tooth  is  the  involute  of  the  pitch-circle  of  the 


wheel.  So  also  is  the  derived  curve,  which  it  is  therefore  unnecessary  to  construct.  The  appearance 
of  the  combination  is  shown  in  Fig.  20S7,  and  it  is  open  to  the  same  objection  as  that  mentioned  in 
regard  to  the  action  of  the  faces  of  the  wheel-teeth  in  Fig.  2080 ;  that  is,  the  whole  wear  is  confined 
to  a  single  point  on  each  pin,  so  that  it  makes  no  difference  whether  the  pin  be  circular  or  not,  as 
it  will  work  equally  well  if  made  with  flat  sides  perpendicular  to  the  pitch  line  of  the  rack. 

Annular  pin-gearing  also  furnishes  two  cases  differing  materially  in  appearance.  If  the  inner 
wheel  be  the  driver,  the  construction  is  as  shown  in  Fig.  20S8,  the  elementary  tooth  P  E  being  the  in- 
ternal epicycloid  generated  by  rolling  the  outer  pitch-circle  upon  the  inner,  and  the  radius  of  the  pin 
being  determined  as  in  Fig.  2085,  the  lettering  corresponding  throughout.  If  the  annular  wheel 
drive,  as  in  Fig.  2089,  the  face  of  its  elementary  tooth  is  the  hypoeycloid  generated  by  rolling  the 
pitch-circle  of  the  pinion  within  that  of  the  outer  wheel ;  and  the  general  construction  will  be  readily 



seen  by  comparing  this  figure  with  the  preceding  one  and  with  Fig.  2085.  If  the  diameter  of  the 
inner  wheel  be  half  that  of  the  annular  one,  the  teeth  of  the  latter  become  radii  of  the  pitch-circle 
if  the  pin  be  a  mathematical  point ;  and  when  it  is  made  of  sensible  diameter,  the  derived  outline 
of  each  tooth  of  the  annular  wheel  is  a  line  parallel  to  its  primitive  radius.     The  arc  of  action  may 


in  this  case  be  made  so  long  that  three  or  even  two  pins  are  sufficient  to  drive  the  outer  wheel  con- 
tinuously, the  whole  combination  in  the  latter  case  assuming  a  very  curious  aspect,  as  shown  in  Fig. 
2090  ;  the  pins  turning  in  blocks  which  slide  back  and  forth  in  the  two  slots  at  right  angles  to  each 
other,  which  are  the  disguised  teeth. 

Spur-Wheek  with  Involute  Teeth. — Next  to  the  cpicycloidal,  the  form  of  tooth  most  extensively 

used  is  that  of  the  involute  of  the  circle.  We  have  seen  that  any  curve  carrying  a  marking-pomt, 
and  rolling  in  contact  with  both  pitch-circles,  may  be  used  to  generate  the  acting  outlines  of  the 
teeth.     Abstractly  speaking,  that  is ;  for  many  curves  which  may  be  thus  generated,  although  they 


geometrically  satisfy  the  conditions,  are  incapable  of  being  practically  used.  Not  so  with  the  invo- 
lute ;  but  though  it  can  be  thus  generated,  its  fitness  for  the  purpose  may  be  much  more  clearly  and 
simply  shown  by  deriving  it  in  another  way.  Let  C,  D,  Fig.  2091,  be  the  centres  of  the  pitch-circles 
LP  (>,  M  I'  X,  in  contact  at  P.  Through  P  draw  A  B  oblique  to  CD,  the  line  of  centres,  and  let 
fall  upon  it  the  perpendiculars  C  B,  D  A,  with  which  as  radii  draw  the  circles  B  8  F,  A  K R.  Sup- 
pose these  circles  to  be  disks  upon  which  is  wound  an  inextensiblc  band  A  B,  carrying  a  pencil  at  A  : 
if  the  upper  one  bi  turned  to  the  left,  it  will  cause  the  lower  one  to  turn  to  the  right,  and  the  pencil 
to  travel  in  the  line  of  the  common  tangent,  as  shown  by  the  arrows  ;  and  in  going  from  A  to  B,  the 
pencil  will  mark  upon  the  planes  of  the  upper  and  lower  wheels  respectively  the  curves  A  F.  KB. 
These  are  the  involutes,  not  of  the  pitch-circles,  but  of  the  base-circles  B  8  F,  A  E  R,  whose  radii 
C B,  D  A  are  to  each  other  in  the  same  ratio  as  C P,  DP,  the  radii  of  the  pitch-circles,  by  reason 
of  the  similar  triangles  P  C  B,  PDA.  By  the  mode  of  generation,  the  arcs  A  E,  B  F  are  equal  to 
A  P  and  therefore  to  each  other  ;  and  the  curves,  being  simultaneously  described  by  a  point  which 
lies  in  the  common  tangent  to  the  base-circle-,  that  is  to  say,  in  the  common  normal  to  the  involutes, 
are  tangent  to  each  other  throughout  the  generation,  and  the  common  normal  always  tuts  CD  at  P. 
These  curves  may  therefore  be  used  as  teeth  for  the  wheels  to  which  they  respectively  belong  ;  thus, 
A  IG,  similar  to  E B,  will  drive  A  J F,  as  indicated  by  the  arrows,  with  a  constant  velocity  ratio, 
the  locus  of  contact  being  A  B.  Now,  because  A  B,  the  line  of  action,  has  a  constant  inclination  to 
T  T,  the  common  tangent  of  the  pitch-circles,  there  is  always  a  certain  fixed  component  of  pressure 
in  the  line  of  centres  CD.  This,  tending  to  cause  wear  in  the  bearings,  is  urged  as  an  objection  to 
this  form  of  tooth  for  heavy  work;  to  which  the  epicycloidal  form  is  not  open,  as  in  that  the  obli- 
quity of  the  common  normal  varies,  and  it  is  perpendicular  to  C  I)  when  the  point  of  contact  reaches 
P.  To  offset  this,  however,  this  form  possesses  some  advantages  The  line  A  I!  was  drawn  at 
pleasure,  and  the  demonstration  in  no  wise  depends  upon  its  inclination  ;  consequently,  for  the  same 
pitch-circles  an  infinite  number  of  base-circles  may  be  used,  or  for  the  same  base-circles  an  infinite 
number  of  pitch-circles  may  be  assigned,  the  only  condition  being  that  the  diameters  shall  have  the 
same  ratio  in  either  case.  Therefore  any  two  wheels  with  involute  teeth  will  gear  together  correctly 
if  the  pitch  be  the  same  in  each;  and  further,  the  velocity  ratio  will  not  be  affected  l>y  changing  the 
distance  between  the  centres,  the  effect  of  which  is  merely  to  alter  the  obliquity  of  the  line  of  action. 
The  backlash  may  therefore  be  reduced  to  a  minimum  by  bringing  the  axes  as  close  together  as  they 
can  be  without  causing  the  teeth  to  bind  ;  and  if  by  wear  of  bearings  the  axes  become  too  wide- 
ly separated,  the  teeth  will  still  gear  correctly  bo  long  as  they  engage  at  all.  None  of  these  things 
can  be  said  in  favor  of  the  epicycloidal  form;  and  moreover,  the  involute  is  essentially  a  strong  form 
of  tooth. 

Since  the  involute  does  not  continue  within  its  circle,  it  is  clear  that  in  Fig;.  20'Jl  A  F,  B  E  arc  the 
greatest  lengths  of  the  acting  faces  that  can  be  used  ;  and  if  they  are  used,  the  tei  th  will  he  pointed, 
as  A  G  U,  B  II  II '.  Considering  D  as  the  driver,  the  action  begins  at  A  ;  and  when  /and  J  meet 
at  /',  the  marking-point  having  traveled  from  A  to  P,  the  curve  I A  will  have  the  position  P  V. 
The  arc  of  approach  A  V  being  thus  equal  to  A  P,  the  arc  of  recess  F_£'must  be  equal  to  PB, 

A  P      AD      P  D 

since  A  E,  the  whole  arc  of  action,  is  equal  to  A  B,  as  before  seen.     But  — _.  =  —  ■ 

J.    H         J5  O  J.     \j 

that  is  to  say,  the  arcs  of  approach  and  of  recess,  if  the  teeth  be  of  the  greatest  possible  length, 
are  to  each  other  as  the  radii  of  the  pitch-circles,  or  as  the  radii  of  the  base-circles,  of  the  driver 
and  the  follower  respectively.  But  as  it  is  not  necessary  that  the  full  length  of  the  curves  should 
be  used,  the  arcs  of  recess  and  approach  may  be  proportioned  at  pleasure  by  properly  adjusting  the 
lengths  of  the  teeth. 

The  diagram,  Fig.  2091,  is  made  without  any  regard  to  practical  proportions,  for  the  sake  of  per- 
spicuity, the  obliquity  of  A  B,  as  well  as  the  pitch,  being  plainly  excessive.  In  practice,  the  angle 
between  A  B  and  ^/'should  never  exceed  20°  if  it  be  possible  to  keep  it  within  that  limit,  and  it 
is  better  that  it  should  be  no  more  than  from  15°  to  17°;  and  the  laying  out  of  working  teeth  is 
illustrated  in  Fig.  2092.  Through  Pare  first  drawn  CD,  the  line  of  centres,  an  arc  of  each  pitch- 
circle,  and  T  T,  the  common  tangent,  from  which  is  measured  the  angle  of  the  line  of  action  A  B, 
which  in  this  case  is  17°,  by  which  the  radii  of  the  base-circles  are  determined.  Then  also  through 
P  are  drawn  P  G  V,  P L  II ,  the  involutes  of  the  lower  and  upper  base-circles.  Supposing  the  num- 
ber of  teeth  to  be  assigned,  the  pitch,  and  the  thickness  of  the  tooth  as  measured  on  the  pitch-circle, 
are  known.  Now,  if  we  assume  the  height  of  the  tooth  of  D,  taking  for  instance  G  as  the  highest 
point,  we  may  find  the  arc  of  action  on  the  right  of  CD  thus  :  Through  0  describe  a  circular  arc 
with  D  as  its  centre,  cutting  A  B,  the  locus  of  contact,  in  /;  then  PI  will  be  equal  to  the  arc  of 
action  on  the  base-circle  through  A,  from  which  that  on  the  pitch-circle  is  readily  found,  subtending 
the  same  angle.  Or  if  that  part  of  the  angle  of  action  be  assumed,  we  can  by  reversing  this  process 
find  PI,  and  thence  determine  G.  Draw  G  D  cutting  the  pitch-circle  in/:  then,  if  PJ  be  just 
half  the  thickness  of  the  tooth,  the  latter  will  be  pointed ;  if  less,  the  tooth  may  be  topped  off  as  in 
the  figure,  while  if  greater  the  assumed  conditions  cannot  be  satisfied.  By  a  proceeding  exactly 
similar,  in  the  case  of  the  upper  wheel,  we  determine  the  height  of  its  tooth  ;  and,  setting  off  from 
P  the  thickness  on  each  pitch-circle,  the  opposite  sides  of  the  teeth  are  bounded  by  similar  and  re- 
versed involutes.  The  clearing  spaces  of  the  upper  wheel  may  be  of  any  forms  which  will  not  touch 
the  epitrochoids  marked  on  the  plane  of  that  wheel  by  the  points  in  the  outer  edge  of  the  tooth  of 
the  lower  one,  and  in  a  similar  manner  the  forms  of  those  in  the  lower  wheel  may  be  determined. 

Rack  and  Wheel  with  Involute  Teeth. — We  have  already  met  with  one  case  in  which  the  tooth  of  a 
wheel  working  with  a  rack,  or  at  least  that  part  of  it  lying  without  its  pitch-circle,  is  of  the  involute 
form.  This  was  shown  in  Fig.  20S0 ;  but,  as  there  pointed  out,  it  was  the  involute  of  the  pitch-cir- 
cle, and  the  action  was  objectionable  as  confining  the  wear  to  a  single  point  of  the  rack-tooth.     A 



better  method  of  constructing  involute  rack-work  is  shown  in  Fig.  2093.  Let  C  be  the  centre  of  the 
pitch-circle  M  P  B,  and  T  T  the  pitch-line  of  the  rack.  Draw  through  P,  the  point  of  contact,  a  line 
of  action  EA  making  any  angle  with  T  T  ;  let  fall  C  A  perpendicular  to  E A,  producing  it  to  cut 

C  4.      Pi 
TT'm  D  ;  then      g ■  =  p-=.     Therefore  a  pencil  at  P,  traveling  from  P  to  A  in  a  right  line  while 

the  rack  moves  through  the  distance  P  D,  the  wheel  turning  also  as  shown  by  the  arrows,  will  trace 
on  the  plane  of  the  rack  the  right  line  D  A,  and  on  that  of  the  wheel  the  involute  B  A  of  the  base- 
circle  A  0.  By  reversing  the  rotation  and  letting  the  pencil  travel  from  P  to  E,  we  should  evident- 
ly obtain  the  extension  B  G  of  the  curve  and  D F of  the  right  line;  and  it  is  equally  clear  that  by 
thus  reversing  the  direction,  the  curve  A  B  G  will  drive  the  rack  to  the  left  with  a  constant  velocity 
ratio,  the  locus  of  contact  being  A  E.  The  point  A  limits  the  top  of  the  rack-tooth  and  the  bottom 
of  the  acting  wheel-tooth,  the  action  in  the  case  above  supposed  beginning  at  A  and  ending  at  E  ; 
the  latter  point  being  found,  if  G  be  assumed,  by  describing  a  circle  through  G  to  cut  the  line  of 
action :  by  drawing  through  E  a  parallel  to  T  T,  we  find  F,  the  point  of  the  rack-tooth  which  will 
meet  G  in  the  action.  So  if  we  assume  /as  the  highest  point  of  the  rack-tooth,  a  parallel  to  T  T 
through  /cuts  E A  in  H,  giving  HP,  which  will  be  equal  to  the  arc  of  action  on  the  right  of  C P, 
measured  on  the  base-circle :  on  the  pitch-circle  or  on  the  pitch-line  of  the  rack,  it  will  be  JP,  found 
by  drawing  ///perpendicular  to  E A,  cutting  T  Tin  J.  If  1  be  assumed,  D  L,  found  by  dropping 
from  /  a  perpendicular  on  T  T,  must  not  be  greater  than  half  the  thickness  of  a  tooth,  and  should 
be  less ;  and  the  same  is  true  of  B  fi,  the  intercept  on  the  pitch-circle  between  B  and  the  radius 
C  G.     As  in  Fig.  2091,  practical  proportions  are  in  this  diagram  disregarded  ;  the  obliquity  of  the 



line  of  action  should  be  no  greater  than  in  the  case  of  two  wheels,  and  the  appearance  of  a  working 
rack  and  wheel  of  this  construction  is  shown  in  Fig.  2094. 

It  may  be  added  that  it  is  possible  also  to  construct  annular  gearing  with  involute  tooth-lines  ;  but 
the  fact  is  of  no  practical  importance,  as  the  teeth  of  the  outer  wheel  will  assume  a  form  very  diffi- 
cult to  make. 

To  find  the  Form  of  a  Tooth  which  shall  gear  correctly  with  one  ichose  Form  is  given. — If  a  tooth 
of  any  reasonable  form  be  given  to  a  wheel,  it  is  possible  to  find  the  curves  which  by  rolling  upon 
the  pitch-circle  shall  generate  the  given  tooth-outline;  and,  by  using  the  same  describing  curves  in 
connection  with  the  pitch-circle  of  another  wheel,  to  construct  a  tooth  which  will  work  correctly  with 
the  first  one.  The  describing  curve  may  or  may  not  be  a  circle ;  but  the  operation  above  described 
is  more  laborious,  and  the  result  less  reliable,  than  the  mechanical  method  illustrated  in  Fig.  2095. 
Let  the  form  of  the  assigned  tooth,  A,  be  accurately  cut  out  as  part  of  a  piece  of  cardboard  of  the 
form  of  a  sector  E E,  whose  centre  is  D,  that  of  the  given  pitch-circle,  MAN;  which  is  to  be 
drawn  on  the  tooth,  cutting  its  outline  at  P.  Cut  out  also  another  sector,  FF,  on  which  describe 
the  pitch-circle  L  O  of  the  other  wheel,  and  also  a  radial  line  C  P.  Draw  on  the  first  sector  the 
radius  DP;  then  by  making  P  on  the  one  coincide  with  Pon  the  other,  and  setting  the  two  radii 
by  the  same  straight-edge,  the  proper  distance  between  the  centres  will  be  fixed,  and  each  sector  mav 
then  be  fastened  to  the  drawing-board  by  a  pin  through  its  own  centre,  being  thus  free  to  turn.  E  E 
being  uppermost,  as  shown,  the  outline  of  the  tooth  is  to  be  traced  on  the  lower  sector.  Then  turn- 
ing it  through  a  small  angle,  F  Fis  to  be  turned  also  through  a  corresponding  angle,  which  will  de- 
pend upon  the  ratio  of  the  diameters  of  the  pitch-circles,  and  the  outline  of  A  traced  again.  By 
marking  on  each  sector  the  angle  subtended  by  a  given  length  measured  on  its  pitch-circle,  and  grad- 
uating its  edge  by  subdividing  this  angle  into  the  same  number  of  equal  parts  on  each  sector,  the 
corresponding  movements  of  the  two  may  be  readily  and  accurately  adjusted  by  reference  to  two 
fixed  marks  on  the  drawing-board,  as  shown  at  P,  S.  Now,  in  every  position  of  A  relatively  to  the 
tooth  with  which  it  is  to  gear,  it  must  be  tangent  to  it  somewhere.  By  tracing  the  outline  of  A 
repeatedly,  we  simply  keep^a  record  of  the  different  positions,  and  by  drawing  a  line  tangentto  them 
all,  as  thus  traced,  we  must  have  the  form  of  the  tooth  to  which  it  was  thus  tangent.  If  this  opera- 
tion be  carefully  performed,  and  a  sufficient  number  of  positions  of  A  traced,  we  shall  find  the  space 



on  the  lower  sector,  between  the  adjacent  teeth  A\  Y,  covered  with  fine  lines,  and  the  forms  of  those 
teeth  accurately  mapped  out. 

Nonsymmetrical  Teeth. — Were  the  two  sides  of  the  tooth  A  in  Fig.  2095  exactly  alike,  it  would 
be  unnecessary  to  map  out  in  the  manner  described  more  than  the  outline  of  the  single  tooth  X. 
Now  it  is  usual  to  make  a  wheel-tooth  symmetrical  about  its  central  radius,  the  opposite  sides  being 
formed  of  similar  curves,  as  we  have  all  along  supposed  to  be  done.  But  this  is  of  course  not  essen- 
tial ;  the  fronts  and  backs  of  the  teeth,  being  entirely  independent  of  each  other,  may  be  formed  by 
using  different  describing  curves :  thus,  as  in  Fig.  2096,  we  may  make  teeth  of  the  involute  form  on 
one  side  and  epicycloidal  on  the  other,  if  for  any  reason  it  should  be  thought  desirable. 

Twisted  Spur-Gearing. — If  we  suppose  a  pair  of  ordinary  spur-wheels  to  be  split  tranversely  into 
thin  laminae,  each  of  these  thin  spur-wheels  will  correctly  drive  the  one  with  which  it  is  in  gear.  If 
in  Fig.  2097  we  suppose  the  laminae  of  which  the  lower  wheel  D  is  composed  to  be  twisted  upon 
each  other  to  the  right,  so  that  each  one  shall  overlap  the  one  below  it  to  the  same  extent,  those  of 
the  other  wheel,  C,  will  be  driven  round  to  the  left.  The  original  tooth-surfaces  of  the  wheels  were 
composed  of  rectilinear  elements  parallel  to  the  axes ;  if  we  suppose  these  lamina?  to  be  of  no  sensi- 
ble thickness,  infinite  in  number,  and  uniformly  twisted  or  rotated  past  each  other,  these  rectilinear 
elements  will  become  helices.  If  the  lamime  be  of  sensible  thickness,  we  shall  have  what  arc  called 
stepped  wheels,  those  which  are  fixed  upon  the  same  axis,  and  constitute  practically  one  wheel,  being 
yet  essentially  distinct  wheels  in  different  phases  of  action ;  nor  is  this  fact  altered  by  any  diminution 
in  the  thickness  of  the  lamina?.  When  that  diminution  reaches  the  limit,  and  the  tooth-surfaces  are 
composed  of  helical  elements,  we  have  what  is  known  as  Hooke's  spiral  gearing,  to  which  we  have 


given  a  different  name,  because  it  is  also  often  but  erroneously  called  wrap-gearing.  The  transmis- 
sion of  rotation  in  this  form  of  gearing  is  due  to  the  successive  action  of  the  laminae  of  one  wheel 
upon  those  of  the  other,  each  in  its  own  plane,  however  thin  they  may  be  supposed,  exactly  as  one 
spur-wheel  acts  upon  another ;  and  not  in  any  manner  or  degree  to  the  helical  form  of  the  elements. 
In  spur-gearing  proper,  the  common  normals  to  the  tooth-surfaces,  which  being  cylindrical  are  tan- 
gent all  along  an  element,  all  lie  in  planes  perpendicular  to  the  axes.  In  twisted  spur-wheels,  the 
helicoidal  tooth-surfaces,  if  tangent  along  any  line,  touch  each  other  along  one  which  will  vary  in 
form  with  the  amount  of  twist  and  also  with  the  actual  form  of  the  transverse  section  or  outline  of 
the  tooth,  and  at  any  rate  partakes  more  or  less  of  the  helical  form.  The  common  normals  will 
therefore  not  lie  in  planes  perpendicular  to  the  axes ;  the  consequence  of  which,  and  of  whatever 
may  be  screw-like  in  the  action  of  the  wheels,  is  to  produce,  not  rotation,  but  end-pressure  in  the 
lines  of  the  axes. 

The  advantage  of  thus  twisting  the  teeth  arises  from  the  fact  that  different  phases  of  the  action 
exist  in  every  position  of  the  wheels  relatively  to  each  other.  The  action  of  a  pair  of  spur-wheels 
is  at  its  best  when  the  point  of  contact  is  on  the  line  of  centres,  or  more  properly,  since  they  have 
sensible  thickness,  when  the  element  of  contact  is  in  the  plane  of  the  axes.  And  if  a  pair  of  spur- 
wheels  of  any  given  thickness  be  twisted  through  angles  measured  by  the  arcs  of  action,  it  is  clear 
that  there  will  always  be  one  point  of  contact  in  the  plane  of  the  axes.  This  being  the  case,  it  fol- 
lows that  if  desired  the  transverse  sections,  or  tooth-outlines,  may  be  such  that  the  action  of  one  upon 
the  other  shall  begin  and  end  upon  the  line  of  centres,  continuing  but  for  one  instant.  This  is  easily 
done,  as  may  be  seen  in  Fig.  2098,  where  both  wheels  are  shown  with  radial  flanks  to  the  teeth. 



Were  the  wheels  to  work  in  the  ordinary  way  as  spur-wheels,  the  faces  of  the  teeth  of  D  should  be 
formed  by  rolling  the  upper  describing  circle  upon  the  lower  pitch-circle  ;  but  now  they  may  be  of 
any  form  that  will  lie  within  the  epicycloids  that  would  be  thus  generated,  but  should  be  tangent  to 
the  radial  flanks  of  D  ;  and  a  similar  argument  holds  in  relation  to  the  upper  wheel.  When  this  is 
done,  the  sliding  disappears,  and  the  wheels  work  in  pure  rolling  contact ;  but  there  is  at  any  instant 
only  a  single  point  of  tangency,  which  must  bear  all  the  pressure,  and  this  travels  along  the  wheels 
from  end  to  end  as  they  turn.  The  action  is,  however,  remarkably  smooth  and  noiseless,  so  that 
such  wheels  are  peculiarly  fitted  for  high  velocities  under  moderate  pressures. 

But,  whatever  the  form  of  the  section,  the  tooth  will  ultimately  become  a  helical  element  of  the 
pitch-cylinder.  In  Fig.  2099,  AB,  C D  are  the  axes  of  the  cylinders  EH,  EI,  tangent  along  the 
element  EL.  Let  the  twist  be  such  that  on  the  lower  cylinder  the  elementary  tooth  shall  be  the 
helix  E  F ;  then  that  upon  the  upper  will  be  the  helix  E  G,  the  axial  advance  being  the  same,  but 
the  perimetral  travel  being  at  rates  which  are  to  each  other  inversely  as  the  diameters  of  the  cylin- 
ders, since  the  arcs  whose  projections  are  L  F,  L  G  must  be  equal  in  length  by  the  mode  of  deriva- 
tion. These  helices  must  coincide  when  developed  upon  the  common  tangent  plane  ;  hence,  if  one 
be  assumed,  the  other  may  be  found  by  developing  the  first  and  then  wrapping  it  upon  the  other 


cylinder.  The  cylinders  in  Fig.  2099  are  externally  tangent,  and  it  is  obvious  that  if  the  helix  on 
one  be  right-handed,  that  on  the  other  will  be  left-handed.  An  annular  wheel,  with  its  pinion,  may 
be  also  made  with  twisted  teeth  in  the  same  manner.  In  this  case,  the  larger  pitch-cylinder  being 
internally  tangent  to  the  smaller,  the  helices  will  be  either  right-handed  or  left-handed  on  both. 
And  it  will  readily  be  seen  that  a  wheel  gearing  with  a  rack  may  be  modified  in  the  same  way:  each 
lamina  of  the  rack  being  advanced  beyond  the  succeeding  one  to  the  same  extent,  in  twisting  the 
wheel  uniformly,  it  is  clear  that  the  tooth-surfaces  of  the  former  will  be  composed  of  right  lines, 
oblique  to  the  plane  of  rotation.  And  when  the  teeth  of  the  wheel  ultimately  become  helical  ele- 
ments of  the  pitch-cylinder,  those  of  the  rack  will  become  right  lines  in  the  tangent-plane,  coinciding 
with  the  developments  of  those  helices.  The  pressure  in  the  direction  of  the  axes,  above  mentioned, 
may  be  neutralized  by  making  each  wheel  in  two  parts,  one  of  which  is  twisted  in  one  direction,  and 
the  other  in  the  opposite. 

On  the  Drawing  of  Epitrochoidal  Curves. — All  curves  traced  by  a  marking-point  carried  by  one 
line  which  rolls  upon  another  are  called  epitrochoids ;  and  among  them  are  the  cyclokl,  epicyloid, 
hypocycloid,  and  involute,  forming  the  outlines  of  the  teeth  of  wheels.     The  following  graphic  pro- 



cesses  will  be  found  of  great  utility  and  convenience  in  many  operations  besides  that  of  drawing  the 
curves  above  mentioned. 

I.  To  find  approximately  the  length  of  a  given  circular  arc. — Let  0,  Fig.  2100,  be  the  centre  of  the 
circular  arc  A  B.  At  A  draw  the  tangent  A  T  ;  draw  the  chord  B  A,  bisect  it  at  I),  and  produce  it 
to  E,  making  A  E  =  A  D.  With  centre  E  and  radius  E B  describe  an  arc  cutting  the  tangent  in 
F.  Then  A  F  will  be  approximately  equal  in  length  to  the  given  arc  A  B.  It  is  stated  by  Frof. 
Rankine,  from  whom  these  processes  are  taken,  that  if  the  angle  A  C  B,  subtended  by  the  given  arc 
be  60J,  A  F  thus  determined  will  be  too  short  by  about  -g\-%  of  its  own  length.  Also,  the  error 
varies  as  the  fourth  power  of  the  angle ;  so  that  if  an  arc  of  30°  be  rectified  by  this  process,  the 
theoretical  error  will  be  reduced  to  j ^J nu- 
ll. On  a  given  circle  to  lay  off  an  arc  approximately  equal  in  length  to  a  given  straight  line. — Let 
the  given  line  A  B,  Fig.  2101,  be  tangent  at  A  to  the  given  circle.  On  A  B  make  A  D  =  }  A  B ; 
with  D  as  centre  and  D  B  =  £  A  B  as  radius,  describe  an  arc  cutting  the  given  circle  in  E ;  then 
will  A  E—  AB,  nearly.  The  error  in  this  construction  is  the  same  as  in  the  preceding  one,  and 
follows  the  same  law.  If  then  A  E,  when  found  as  above,  subtends  an  angle  of  more  than  about 
60°,  the  given  line  .4  2?  may  be  subdivided,  and  the  arc  corresponding  to  any  fraction  of  it  determined. 
III.  To  find  the  radius  of  a  circle  on  which  an  arc  of  a  given  length  shall  measure  a  given  angle. — 
Let  A  B,  Fig.  2102,  be  the  length  of  the  arc.  Draw  the  indefinite  line  A  G,  making  the  angle  BAG 
half  the  given  angle ;  also  draw  A  II  perpendicular  to  A  B.  Set  off  as  before  A  I)  =  $  A  B,  and 
with  centre  I)  and  radius  I)  B  describe  an  arc  cutting  A  G  in  E.  Bisect  A  E  by  a  perpendicular 
cutting  A  II  in  V ;  then  A  C  is  the  radius  sought.  For,  drawing  the  arc  ^4  JFand  the  radius  CE, 
the  angle  B  A  E,  between  the  chord  and  the  tangent,  is  half  the  angle  A  C  E  at  the  centre. 

This  being  only  an  application  of  the  preceding  process,  and  involving  the  same  error,  if  the  given 
angle  be  over  60°,  both  it  and  the  given  line  should  be  subdivided.  By  this  method  we  may  readily 
find  the  diameter  of  a  circle  when  the  circumference  is  given;  for,  making  A  B  one-sixth  of  the 
given  circumference,  and  the  angle  B  A  0  equal  to  30°,  we  at  once  have  A  E  the  radius. 

The  Cycloid. — Let  the  circle  whose  centre  is  O,  Fig.  2103,  roll  on  the  right  line  A  B,  to  which  it 
is  tangent  at  P;  then  a  marking-point  at  O  in  the  circumference  will  trace  the  cycloid  ORB. 
Divide  the  semi-circumference  F  0  into  equal  parts  at  1,  2,  3,  etc.;  set  off  PI)  equal  to  this  semi- 
circumference,  and  divide  it  into  the  same  number  of  equal  parts  at  the  points  correspondingly  num- 
bered. The  number  of  subdivisions  is  immaterial;  practically  the  six  shown  are  sufficient  and  the 
most  readily  made,  PI)  being  found  by  rectifying  P  2  as  above  explained,  and  setting  off  the  length 

thus  determined  three  times  from  P. 
The  points  1,  2,  3,  etc.,  on  the  circle, 
will  come  successively  into  contact 
with  the  points  1',  2',  3',  etc.,  on  the 
tangent ;  and  the  centre,  traveling 
in  the  line  parallel  to  A  B,  will  be 
always  vertically  over  the  point  of 
contact.  Thus,  when  C2  becomes 
the  contact-radius,  it  will  have  the 
position  E2' ;  when  6' 4  is  the  con- 
tact-radius, the  centre  will  be  at  F, 
and  so  on.  But  the  distance  from  O 
to  the  point  2  on  the  circle  is  the 
same  when  the  centre  is  at  E  as  when 
it  is  at  C:  if  then  we  set  off  from 
the  point  2'  on  the  tangent  the  chord 
2'  R  =  O  2  on  the  circle,  ER  will  be 
the  position  of  the  generating  radius 
C  O  for  that  position  of  the  circle, 
and  R  a  point  on  the  cycloid.  When 
C  has  reached  F,  04  being  contact-radius,  the  generating  radius  will  be  F S,  the  chord  4'  S  being 
made  equal  to  the  chord  04 ;  and  in  like  manner  any  number  of  points  may  be  found.  When  O 
reaches  D,  the  radius  C  O  will  have  the  inverted  position  G  D,  to  which  the  cycloid  is  tangent  at  D. 
The  rolling  motion  of  the  circle  is  compounded  of  a  rotation  on  its  axis  and  a  bodily  translation 
in  the  direction  C  G.  We  may  imagine  these  motions  to  take  place  separately  and  successively, 
instead  of  simultaneously,  and  thus  find  points  in  the  cycloid  in  another  way.  If,  for  instance,  we 
suppose  the  circle  to  be  turned  round  its  centre  C  until  0  2  takes  the  place  of  C  P,  this  will  bring 
the  generating  radius  C  O  to  the  position  04;  if  we  then  push  the  circle  forward  through  a  dis- 
tance C E equal  to  the  arc  2  Por  04,  we  shall  have  the  generating  radius  ER  in  its  correct  posi- 
tion, parallel  to  C4.  So  also  if  0  be  turned  round  C  to  the  point  2  on  the  circle,  and  then  pushed 
forward  to  S,  the  distance  2  S  being  equal  to  the  arc  0  2,  then  S  will  be  a  point  on  the  cycloid. 

But  a  more  rapid  and  accurate  method  of  drawing  the  curve  is  by  means  of  tangent  arcs.  This 
method  depends  on  the  fact  already  stated,  that  in  rolling  contact  the  point  of  tangency  is  in  the 
instantaneous  axis.  Thus,  in  the  original  position  of  the  circle,  P  is  the  instantaneous  centre;  and 
when  the  circle  begins  to  roll,  every  point  in  or  connected  with  it  is  at  the  instant  in  the  act  of 
describing  a  circle  of  which  P  is  the  centre.  If  then  we  describe  an  arc  about  P  with  radius  OP, 
the  direction  of  that  arc  is  also  the  direction  of  O's  path  at  that  instant.  When  02  becomes  the 
contact-radius,  the  instantaneous  centre  will  be  the  point  2'  on  A  B.  But  as  the  chord  0  2  of  the 
circle  does  not  change  its  length,  it  must  then  be  the  instantaneous  radius  ;  therefore,  if  about  2'  on 
the  tangent,  with  radius  2'  R=  0  2,  we  describe  an  arc,  it  also  will  coincide  in  direction  with  the 
path  of  0  at  the  instant.     Now  the  direction  of  a  curve  at  any  point  is  that  of  its  tangent  at  that")'' 



point ;  and  these  arcs  being  traced  by  0,  which  also  traces  the  cycloid,  it  follows  that  the  latter 
curve  is  tangent  to  the  arcs.  If  then  we  take  as  centres  the  points  1',  2',  3',  etc.,  on  A  B,  and  about 
them  describe  arcs,  using  as  radii  the  chords  0  1,  0  2,  etc.,  the  envelope  of  these  arcs,  or  curve  tangent 
to  them  all,  will  be  the  cycloid.  And  these  arcs  serve  better  as  guides  in  drawing  the  curve  than 
actual  points  would,  since  they  do  give  an  indication  of  its  direction,  while  the  points  do  not.  By 
making  a  greater  number  of  subdivisions  and  striking  a  greater  number  of  arcs,  the  cycloid  may  be 
mapped  out  with  any  desired  degree  of  precision,  though  not  a  single  point  be  found.  Should  the 
point  of  the  curve  corresponding  to  any  point  of  contact,  as  for  instance  2'  on  A  B,  be  required,  it  is 
quickly  found  by  erecting  the  perpendicular  2'  E  to  locate  the  centre,  and  cutting  the  cycloid  by  an 
arc  of  the  describing  circle,  which  will  of  course  give  R  the  extremity  of  the  instantaneous  radius 
for  the  point  selected.  This  instantaneous  radius  is  of  course  the  normal,  and  T  R  7' perpendicular 
to  it  is  the  tangent,  to  the  cycloid  at  R  ;  and  the  radius  of  curvature  is  R  L,  found  by  prolonging 
and  doubling  R  2' ;  so  also  M S,  twice  the  instantaneous  radius  4'  S,  is  the  radius  of  curvature  at  S. 
The  Epicycloid. — This  curve  is  traced  by  the  rolling  of  a  circle,  not  upon  a  base-line,  but  upon  the 
outside  of  a  base-circle.  In  Fig.  2104,  H  is  the  centre  of  the  base-circle,  C  that  of  the  rolling  one, 
in  the  circumference  of  which  is 

O,  the  marking-point.     P  being  n  2104. 

the  point  of  contact  at  starting, 
the  radii  C  P,  PHWc  in  one  right 
line;  and  as  the  point  of  contact 
must  always  lie  on  the  line  of  cen- 
tres, when  C  reaches  E  the  line 
EH  will  cut  the  base-circle  A  PB 
at  2',  the  point  of  contact  then, 
and  P  2'  must  be  equal  to  the  arc 
P  2  which  has  rolled  over  it,  and 
the  path  of  C  will  be  a  circle  whose 
centre  is  H.  The  first  step  then 
is  to  subdivide  the  semi-circumfer- 
ence P  0  into  equal  parts  at  the 
points  2,  4  (a  greater  number  be- 
ing of  course  used  in  practice ;  but 
the  analogy  to  the  preceding  figure 
is  so  close  that  what  is  here  shown 
will  suffice  for  illustration).  On 
the  left  is  shown  the  operation  of 
rectifying  P  V,  an  arc  equal  to 
P  2,  on  the  common  tangent  P  T, 
and  of  setting  off  on  the  base-cir- 
cle an  arc  P  W  equal  to  the  length 
thus  found  and  therefore  to  P2. 
Equal  arcs  P  2',  2'  4',  4'  D,  being 
then  set  off  from  P  toward  B,  we 
have  P  D  equal  to  the  half  cir- 
cumference P  0.  Now,  when  C  2 
is  contact-radius,  E  must  be   the 

centre  of  the  describing  circle ;  and  making  2'  R  —  2  0,  we  have  R,  a  point  in  the  curve.  Other- 
wise, the  rolling  being  now  compounded  of  a  rotation  about  C  and  a  revolution  about  H,  we  may 
first  turn  the  circle  in  its  original  position  until  2  reaches  P,  which  will  bring  0  to  4  ;  then  a  circu- 
lar arc  through  4  with  centre  //will  cut  the  describing  circle  in  its  second  position  at  R. 

But,  again,  the  method  of  tangent  arcs  may  be  used.  When  C  2  becomes  contact-radius  at  E2',  the 
point  of  contact  2'  is  the  instantaneous  centre,  2'  R  equal  to  2  O  is  the  instantaneous  radius,  and 
the  curve  will  be  tangent  to  the  circular  arc  thus  determined  ;  and  by  repeating  this  as  in  the  case 
of  the  cycloid,  the  curve  may  be  most  expeditiously  mapped  out,  without  finding  a  point  in  it.  If 
the  radius  of  curvature  at  any  point,  R  for  instance,  be  required,  an  arc  described  about  R  with  the 
radius  of  the  rolling  circle  will  give  by  its  intersection  with  0  G  the  path  of  the  centre,  the  position 
of  the  latter  when  the  marking-point  is  at  R.  Then  E  H  determines  2',  the  corresponding  point  of 
contact,  and  the  position  R2l  of  the  instantaneous  radius,  normal  to  the  curve.  Prolong  R2'  inde- 
finitely, draw  R  E  the  generating  radius,  and  HI  parallel  to  it.  Bisect  2'  H'm  K,  draw  RK  and 
produce  it  to  cut  H I'm  L,  and  draw  L M parallel  to  HE,  which  will  cut  the  prolongation  of  R  2'  in 
21,  the  centre  of  curvature. 

The  Hypocycloid. — This  is  generated  by  a  marking-point  in  the  circumference  of  a  circle  which 
rolls  on  the  inside  of  another  of  greater  diameter."  The  construction  is  illustrated  in  Fig.  2105, 
which  is  lettered  throughout  to  correspond  with  Fig.  2104;  and  the  steps  of  the  process  being  iden- 
tical, including  the  finding  of  the  radius  of  curvature,  no  further  explanation  is  necessary. 

The  Internal  Epicycloid. — If  one  circle  be  internally  tangent  to  another,  and  the  greater  roll  upon 
the  less,  a  marking-point  in  its  circumference  will  trace  what  is  called  the  internal  epicycloid,  merely 
to  call  attention  to  the  particular  mode  of  generation.  For  it  is  to  be  noted  that  every  epicycloid 
may  be  generated  by  the  rolling  upon  the  same  base-circle  of  either  of  two  circles ;  and  the  same  is 
true  of  the  hvpocyeloid.  Thus,  in  Fig.  2106,  in  the  diagram  on  the  left,  let  D  be  the  centre  of  the 
base-circle,  arid  C  that  of  one  which  by  rolling  upon  it  will  generate  the  epicycloid  shown,  the  tan- 
gency  being  external.  Then  the  same  curve  will  also  be  traced  by  the  rolling  upon  D  of  the  circle 
E,  to  which  it  is  internally  tangent ;  the  diameter  of  this  larger  circle  being  equal  to  the  sum  of  the 



diameters  of  the  other  two.  Thus  every  internal  epicycloid  is  also  an  external  one  ;  but  the  epitro- 
choids  traced  by  points  carried  by  these  different  describing  circles,  not  on  their  circumferences,  will 
not  be  the  same.  In  the  diagram  on  the  right,  D  is  the  centre  of  the  large  base-circle,  within  which 
are  shown  two  describing  circles,  the  sum  of  their  diameters  equaling  the  diameter  of  D  ;  and  the 

same  hypocycloid  will  be  traced  by  the 
rolling  of  cither  of  them  within  the  out- 
er circle.  In  both  these  eases,  if  the 
curve  be  traced  in  a  given  direction,  the 
two  circles  by  which  it  may  be  gener- 
ated will  roll  in  opposite  directions. 

The  Epitrochoid. — It  is  evident  that 
the  marking-point  carried  by  a  rolling 
circle,  or  other  line,  need  not  be  in  the 
rolling  line.  Although,  as  above  stated, 
the  term  epitrochoidal  is  applied  in  g<  n- 
eral  to  all  lines  generated  by  marking- 
points  so  controlled,  yi't  the  name  epi- 
trochoid is  also  specifically  applied  in 
the  ca-^e  in  which  the  point  is  carried 
by  one  circle  rolling  upon  another,  and 
is  not  situated  in  the  circumference.  If 
it  be  outside  the  rolling  circle,  the  curve 
is  called  a  curtate  epitrochoid,  and  is 
looped,  as  shown  in  Fig.  '2107.  If  the 
marking-point  be  within  the  rolling  cir- 
cle, as  in  Fig.  2108,  the  curve  is  waved, 
the  marking-point  never  reaching  the 
base-circle,  and  is  called  jn-olalc.  The 
epicycloid  is  therefore,  it  will  be  seen, 
but  a  special  case,  being  the  boundary 
between  these  two  forms ;  and  the  mark- 
ing-point just  reaching  the  base-circle, 
there  is  neither  wave  nor  loop,  but  the 
curve  is  tangent  to  the  radius  G  D,  the 
adjacent  branches  forming  a  cusp.  The 
construction  by  points  is  almost  self-evident ;  the  position  of  the  generating  radius,  being  controlled 
by  the  rolling  circle,  is  determined  exactly  as  in  the  previous  cases,  and,  its  length  being  constant, 
points  in  either  of  these  curves  arc  found  as  readily  as  in  the  others.  And  it  will  be  at  once  seen 
by  these  figures  that  the  method  by  tangent  arcs  is  of  perfectly  general  application,  in  drawing  all 
curves  capable  of  being  thus  generated. 
The  point  of  contact  at  any  instant  is  the  0 

centre  of  rotation  at  that  instant,  and  the 
distance  to  the  marking-point  is  the  in- 
stantaneous radius,  with  which  the  tan- 
gent arc  is  to  be  described. 

The  Involute  of  the  Circle. — This  may 
be  considered  in  a  sense  the  converse  of 
the  cycloid,  being  generated  by  a  point 
in  a  right  line  rolling  upon  a  circle.  Or, 
what  amounts  to  the  same  thing,  if  a  pen- 
cil be  fixed  at  the  end  of  an  inextensible 
string  of  no  sensible  thickness,  and  the 
string  be  wound  upon  or  unwound  from 
a  circle,  being  held  taut,  it  will  trace  the 
curve  in  question.  It  is  easily  construct- 
ed, as  in  Fig.  2109.  The  circumference 
being  divided  into  equal  parts  at  the 
points  0,  1,  2,  etc.,  a  tangent  is  drawn  at  each  point,  and  on  it  is  set  off  the  length  of  the  arc  meas- 
ured from  the  point  of  starting  to  the  point  of  tangency.  Thus,  let  the  semi-circumference  be  unwound 
to  the  right,  beginning  at  O  ;  then  the  tangent  1  1  is  made  equal  to  the  arc  O  1,  the  tangent  2  2  to  the 
arc  0  2,  and  so  on.     The  method  of  tangent  arcs  may  also  be  used  here.     The  points  1,  2,  3,  etc.,  on 



the  circle  being  the  instantaneous  centres,  the  tangents  1  1,  2  2,  etc.,  are  the  instantaneous  radii. 
These  tangents  are  also  not  only  the  normals  to  the  curve,  but  also  the  radii  of  curvature  at  the  cor- 
responding points. 

Of  Circular  and  Diametral  Pitch. — The  term  pitch,  as  has  been  explained,  is  used  to  denote  the 
distance,  measured  on  the  pitch-circle,  which  is  occupied  by  a  tooth  and  a  space  ;  or  in  other  words, 
the  arc  found  by  dividing  the  circumference  into  as  many  equal  parts  as  there  are  teeth  in  the  wheel. 

We  have,  then :  Pitch  x  number  =  circumference  ;  whence,  if  either  two  factors  be  given,  we  readily 
find  the  third.  It  is  clearly  more  convenient  to  express  the  pitch  in  whole  numbers  or  manageable 
fractions,  as  2-inch  pitch,  U-inch  pitch,  and  so  on.  But  the  circumference  being  3.1416  times  the 
diameter,  it  happens  that  if  this  system  be  adopted,  the  diameter  of  the  pitch-circle  will  often  involve 
an  awkward  decimal.  The  pitch  as  above  defined  is  styled  the  circular  pitch,  in  order  to  distinguish 
it  from  what  is  called  the  diametral  pitch,  the  use  of  which  is  designed  to  avoid  the  inconvenient 
fractions  above  mentioned,  and  otherwise  to  facilitate  the  necessary  calculations.  The  diametral 
pitch  is  simply  the  quotient  found  by  dividing  the  diameter  of  the  pitch-circle,  instead  of  the  circum- 
ference, by  the  number  of  teeth.     Its  relation  to  the  circular  pitch  is  clearly  seen  thus : 

Circular  pitch  = 

Diametral  pitch 

diameter  x  3.1416 

number  of  teeth 

Circular  pitch 



number  of  teeth 

In  the  practical  use  of  this  system,  values  of  the  diametral  pitch  are  selected,  being  fractions  hav- 
ing unity  for  the  numerator  and  a  whole  number  for  a  denominator  in  each  case,  as  $,  \,  -fa,  ^4,  etc. 

The  denominators  of  these  fractions  are  evidently  the  corresponding  values  of 

number  of  teeth 


are  used  to  designate  the  wheels ;  thus,  a  "4-pitch  wheel  "  is  one  of  which  the  diametral  pitch  is  }, 
and  so  on.  Suppose,  for  example,  that  we  wish  to  know  the  diameter  of  a  wheel  of  40  teeth,  of  "  5- 
pitch"  :  we  have  ^fl  =  8  =  diameter  of  pitch-circle.  Or  if  the  number  of  teeth  of  "S-pitch"  in  a 
wheel  of  174  diameter  is  desired,  we  have  8  x  11$  =  140  =  number  of  teeth. 

The  advantage  of  this  system  lies  in  the  obvious  fact  that  it  is  practically  more  important  to  have 
the  diameter  of  the  pitch-circle  either  a  whole  number  or  a  convenient  fraction,  than  that  the  cir- 
cular pitch  should  be  either. 


Bevel-wheels  are  used  for  the  transmission  of  motion  from  one  axis  to  another  which  intersects  it. 
•They  are  also  called  conical  wheels,  because  the  pitch-surfaces  are  cones,  whose  common  apex  is  the 
intersection  of  the  axes.  It  is  usually  the  case  in  practice  that  the  positions  of  the  axes  are  given, 
and  it  is  required  to  make  the  wheels  so  as  to  preserve  a  given  velocity  ratio.  The  first  step  is  to 
find  the  forms  of  the  pitch-cones.  In  Fig.  2110,  let  A  B,  CD  be  the  axes,  meeting  at  V;  and  let 
us  suppose  that  two  revolutions  of  the  former  are  to  produce  three  revolutions  of  the  latter.  Draw 
a  line  n  n,  parallel  to  A  B,  and  at  a  distance  from  it  measuring  3  on  any  convenient  scale  of  equal 
parts ;  also  a  line  m  m,  parallel  to  C  D,  and  at  a  distance  from  it  equal  to  2  on  the  same  scale.  These 
lines  intersect  at  P  ;  and  drawing  VP,  we  see  that  it  will  by  revolving  around  A  B  generate  one 
cone,  while  if  it  revolve  around  CD  it  will  generate  another,  the  two  being  tangent  alone;  V P ;  and 
these  are  the  pitch-cones  required.  The  line  mm  is  here  drawn  within  the  angle  B  V  D :  had  it 
been  drawn  within  the  angle  A  V D,  as  in  Fig.  2111,  we  should  have  had  a  different  pair  of  cones; 
the  velocity  ratio  is  the  same  in  either  case,  but  it  will  be  seen  that,  supposing  A  B  to  rotate  in  the 
same  direction  in  both  instances,  the  rotations  of  CD  are  in  opposite  directions.  Now,  only  limited 
portions  (frusta)  of  these  cones  need  or  can  be  employed,  as  shown  in  the  figures.  Their  distance 
from  the  vertex  is  immaterial,  so  far  as  the  theory  is  concerned  ;  and  this,  which  also  determines  the 
actual  size  of  the  wheels,  is  usually  decided  by  considerations  connected  with  the  framing  of  the  ma- 
chine or  the  power  to  be  transmitted,  with  neither  of  which  we  have  to  do  in  ascertaining  the  forms 
of  the  teeth.     If  one  shaft  can  be  carried  past  the  other,  however,  we  see  that  we  have  the  choice 



between  two  pairs  of  wheels,  each  giving  the  same  velocity  ratio,  but  differing  in  regard  to  the  direc- 
tions of  the  rotations.  The  choice  here  is  also  usually  determined  by  the  conditions  of  the  machine 
in  which  the  wheels  are  to  be  used  ;  we  will  therefore  suppose  that  the  pair  shown  in  Fig.  2110  has 
been  selected,  and  that  the  teeth  arc  to  be  laid  out. 

The  manner  in  which  this  is  usually  done  is  as  follows:  In  Fig.  2112,  V  P  E,  V  P II  are  the  pitch- 

cones,  V  P  being  the  common  element,  which  and  the  axes  arc  in  the  plane  of  the  paper.  Draw 
through  Pa  perpendicular  to  V P,  cutting  A  B  at  /'and  CD  at  G.  Then,  if  Pi*' revolve  around 
A  B,lt  will  generate  a  cone  P  F E,  whose  elements  are  normal  to  those  of  V P E.  So  also  P  G  by 
revolvin"  around  CD  generates  a  cone  P  G  II,  normal  to  Y  P II.     These  normal  cones  are  now  to 

be  developed.  It  is  clear  that  if  F  G 
be  the  trace  of  a  plane  perpendicular  to 
the  paper,  it  will  be  tangent  to  both  ; 
and  the  right-hand  part  of  the  diagram 
shows  the  development  of  the  cones  upon 
it.  The  vertices  appear  as  the  points 
/,  K;  the  base  of  the  upper  cone  will  be 
a  part  of  the  circle  L  J/,  \\  hose  radius 
is  /•'/',  and  that  of  the  lower  will  be  a 
part  of  the  circle  N  O,  whose  radius  is 
0  /'.  Upon  these  circles  teeth  are  to  be 
laid  out  as  if  they  were  the  pitch-circles 
of  spur-wheels,  being  usually  made  of 
the  epieycloidal  form.  Were  the  whole 
surface  of  a  normal  cone  developed,  all 
the  teeth  laid  out,  a  thin  sheet  of  metal  cut  to  the  foim  thus  found,  and  then  wrapped  back  upon 
the  cone,  we  should  then  have  the  outlines  of  the  teeth  on  the  larger  end  of  the  wheel.  But  in  order 
to  make  the  drawings,  we  need  only  lay  out  a  single  tooth  on  the  development  of  each  cone.  Now 
the  pitch  is  the  same  on  both  wheels,  "and  when  we  have  decided  on  t  e  number  of  teeth,  we  know 
what  it  will  be.     We  have  then  only  to  rectify  such  a  fraction  of  the  base-circle  of  either  cone,  EP 

for  instance,  as  will  contain  the  pitch  any  convenient  number  of  times,  set  off  on  each  circle  in  the 
development  from  the  point  of  contact  an  arc  equal  in  length  to  this  rectification,  by  the  processes 
already  described,  and  divide  each  of  these  arcs  into  the  same  number  of  equal  parts,  to  obtain  the 
correct  pitch  on  the  developed  bases  and  construct  the  teeth  Supposing  this  to  be  done,  the  mode 
of  completing  the  drawing  of  the  larger  wheel  is  shown  in  Fig.  2113. 



It  is  evident  that,  as  the  teeth  project  beyond  the  pitch-cone,  both  it  and  the  normal  cone  must  be 
enlarged  beyond  the  original  dimensions.  Thus  F P  must  be  extended  till  FD  is  equal  to  the  ex- 
treme radius  of  the  developed  tooth,  which  is  projected  back  upon  it,  and  the  blank  for  the  wheel 
will  consist  of  a  frustum  of  the  cone  D  V  H,  joined  to  a  frustum  of  the  normal  cone  1)  F H.  The 
bottom  of  the  space  in  the  development  is  also  projected  back  upon  F P  at  F,  and  the  top  and  bottom 
of  the  tooth  will  be  bounded  in  the  section  shown  in  the  lower  half  of  the  side  view  by  the  lines 
D  G,  E  A",  converging  in  V.  Having  decided  on  the  length  P  P  of  the  tooth,  the  inner  end  is  lim- 
ited by  another  cone  normal  to  the  pitch-cone,  generated  by  a  line  through  P  perpendicular  to  V  P. 

If  a  side  elevation  is  to  be  drawn,  the  end  view  must  be  first  constructed.  The  points  Z>,  P,  F,  in 
revolving  around  the  axis,  describe  circles  which  correspond  to  certain  circles  in  the  development. 
Thus  P  describes  the  base  of  the  pitch-cone,  which  develops  into  L  M.  In  the  end  view,  whose  cen- 
tre is  C,  this  circle  is  seen  in  its  true  size ;  and  the  breadth  of  a  tooth  or  of  a  space  measured  on 
this  circle  must  be  the  same  as  the  breadth  measured  on  L  M.  Similarly  the  breadth  on  the  outer  or 
inner  circles,  described  by  D  and  F,  must  be  the  same  as  on  the  corresponding  circles  in  the  develop- 
ment. Since  the  arcs  are  equal,  but  the  radii  different,  the  chords  will  not  be  equal :  practically, 
however,  the  difference  will  not  be  appreciable  unless  the  wheel  be  of  great  size  or  the  pitch  very 
coarse ;  and  by  the  processes  of  rectification  and  its  converse,  previously  explained,  the  difference 
may  be  determined  graphically  if  desired.  Intermediate  circles  may  be  drawn  in  the  development 
and  in  the  projections,  and  similarly  used,  for  determining  the  breadth  of  the  tooth  at  other  points, 
and  thus  fixing  the  outline  with  precision.  The  form  at  the  inner  end  is  precisely  similar  but  smaller, 
and  is  constructed  by  drawing  radial  lines  to  cut  the  series  of  smaller  circles  described  by  the  points 
G,  P,  K.  The  radius  of  any  intermediate  circle  in  the  development  being  projected  on  FD,  and  a 
line  drawn  from  the  point  thus  found  toward  V,  cutting  G  A",  we  shall  have  the  point  which  will 


describe  the  corresponding  intermediate  circle  at  the  inner  end  of  the  tooth.  The  drawing  of  one 
tooth  in  the  end  view  being  completed,  the  others  are  copied  in  their  proper  positions,  and  the  various 
points  projected  to  the  corresponding  circles  in  the  side  elevation,  where,  being  seen  edgewise,  they 
appear  simply  as  right  lines,  G  J,  D  H,  etc.  Since  all  the  elements  of  the  tooth-surfaces  converge 
in  V,  it  is  better  here  also  to  determine  only  the  forms  of  the  teeth  at  the  outer  end  by  projection 
from  the  end  view,  and  to  draw  converging  lines  toward  V  to  find  such  outlines  as  may  be  visible  at 
the  inner  end. 

This  method  of  laying  out  the  teeth  is,  however,  only  approximately  correct.  In  spur-gearing  the 
tooth-surface  is  generated  by  the  element  of  a  describing  cylinder  rolling  in  contact  with  the  pitch- 
cylinder  ;  and  it  can  be  shown  that  in  an  analogous  manner  the  tooth-surface  should  be  generated  by 
the  element  of  a  describing  cone  rolling  with  the  pitch-cone.  By  following  the  motion  of  the  describ- 
ing element  of  this  auxiliary  cone,  and  finding  the  points  in  which  in  different  positions  it  pierces  the 
normal  cone,  we  can  construct  the  trace  upon  the  latter  of  the  surface  thus  generated,  or  in  other 
words  the  outline  of  the  correct  tooth.  The  error  of  the  method  first  described,  then,  consists  in  the 
assumption  that  this  outline  when  developed  will  be  a  true  epicycloid,  hypocycloid,  or  involute,  as  the 
case  may  be. 

In  Fig.  2114,  P  V H  is  a  pitch-cone,  P  F H  its  normal  cone,  and  P  V  G  a,  describing  cone,  which 
by  rolling  on  the  outside  of  P  V H  will  generate  the  surface  of  the  face  of  the  tooth.  The  normal 
cone  is  to  be  extended  as  far  as  may  be  necessary  to  determine  the  line  in  which  the  describing  cone 
intersects  it ;  in  the  side  view  this  line  is  P  T  G,  and  in  the  end  view,  which  is  a  projection  on  a 
plane  perpendicular  to  VF  (the  axis  of  the  pitch  and  normal  cones),  it  appears  as  the  curve  P  T  G  U. 
Now,  taking  P  F,  the  common  element  at  starting,  for  the  describing  line,  it  is  clear  that  if  the  cone 
V P  G  were  to  turn  while  the  normal  cone  did  not,  that  element  would  trace  on  the  latter  merely 
this  line  of  intersection.  But  the  normal  cone  does  turn,  and,  the  ratio  of  the  two  velocities  being 
known,  we  can  easily  find  the  actual  trace  of  FPupon  it  by  the  aid  of  this  line  of  intersection. 



Thus,  let  the  lower  cone  turn  until  D  P  appears  in  the  end  view  as  D  1' ;  then  the  upper  cone  will 
have  turned  through  the  known  angle  P  V\,  and  the  curve  1  1'  must  meantime  have  been  traced 
upon  it.  So  when  I)  P  has  gone  to  I)  2',  P  V  will  have  gone  to  1'  2,  and  the  curve  2  2'  will  have  been 
traced,  and  so  on. 

As  an  illustration  of  the  extent  of  the  error  in  the  approximate  method,  we  show  in  Fig.  2115  a 
full-size  outline  of  a  tooth  as  determined  by  it,  and  also  as  found  by  the  process  just  explained. 


The  wheel  is  one  of  30  inches  diameter,  with  21  teeth.  The  describing  cone  was  taken  of  the 
diameter  which  would  generate  a  flank  surface  most  nearly  approximating  to  a  plane,  the  difference 
being  inappreciable  within  the  limit  of  the  depth  of  the  clearing  space  ;  and  this  being  designed  to 
gear  with  another  wheel  exactly  similar,  the  same  describing  cone  was  used  for  the  face  of  the  tooth 
also.  The  form  of  the  tooth  which  would  be' determined  under  these  conditions  by  the  first  method 
is  shown  in  dotted  lines ;  the  full  lines  being  of  the  correct  form  as  found  by  the  second  method. 
The  discrepancy  is  quite  marked,  and  sufficient  to  make  a  material  difference  in  the  smoothness  of 
the  action  and  in  the  durability  of  the  wheels. 

It  was  remarked  in  connection  with  Figs.  2110  and  2111  that,  with  a  given  pair  of  axes  and  a 
given  velocity  ratio,  it  is  always  possible  to  construct  two  pairs  of  pitch-cones,  of  which  the  direc- 
tional relations  are  different.  Of  these,  one  pair  will  always  be  in  external  contact;  but,  as  shown 
in  Fig.  2116,  the  other  pair  may  be  such  that  one  of  the  two  shall  touch  the  other  internally.  In 
this  case  the  methods  of  constructing  the  teeth  will  be  analogous  to  those  used  in  annular  spur-gear- 
ing. Or  again,  as  in  Fig.  2117,  the  common  element  V  P,  as  determined  by  the  process  described, 
may  be  perpendicular  to  one  of  the  axes,  the  pitch-cone  thus  degenerating  into  a  plane.     The  normal 



cone  then  becoming  a  cylinder,  its  base  will  develop  into  a  right  line,  and  the  construction  of  tho 
teeth  by  the  first  method  will  be  similar  to  that  applicable  in  the  case  of  a  rack  and  wheel. 

Twisted  Bevel-  Wheeh. — We  may  suppose  a  pair  of  bevel-wheels  to  be  cut  transversely  into  thin 
lamina?,  as  we  did  in  the  case  of  two  spur-wheels.  Each  of  these  thin  wheels  will  drive  its  mate,  and 
as  before  we  may  twist  them  round  so  that  each  one  shall  overlap  the  next  one  on  the  same  axis,  to 
the  same  angular  extent.  Supposing  the  laminae  to  be  of  inappreciable  thickness,  we  shall  thus 
transform  the  converging  rectilinear  elements  of  the  tooth-surfaces  into  conical  helices ;  and  if  the 
teeth  be  now  made  indefinitely  small  and  numerous,  they  will  ultimately  become  such  conical  helices 
lying  on  the  pitch-surfaces,  as  shown  in  Fig.  2118.  We  may  thus  attain  in  bevel-gearing  the  same 
advantages  that  were  shown  to  belong  to  twisted  spur-gearing.  Nor  would  it  be  difficult  to  make  the 
teeth  of  this  form  in  any  engine  in  which  it  is  possible  to  cut  bevel-gearing  correctly.  Spur-wheels, 
as  is  well  known,  may  be  cut  with  precision  by  a  milling-cutter  whose  outline  is  that  of  the  space 
between  two  teeth,  because  the  elements  of  the  teeth  are  parallel  to  the  axis,  and  the  space  every- 
where of  the  same  size  and  form.  But  the  space  between  two  teeth  of  a  bevel-wheel  continually 
changes  its  size,  and  though  the  outlines  of  parallel  sections  are  all  similar,  they  are  of  different 
curvatures.  Consequently  the  teeth  can  only  be  formed  accurately  by  planing,  as  in  the  cutting 
engine  of  Corliss,  the  tool  traveling  always  in  a  line  toward  the  vertex  of  the  pitch-cone.  Now,  if 
the  blank  be  made  to  rotate  uniformly  during  each  cut,  the  desired  twist  may  be  given  to  the  teeth 
with  ease  and  perfect  accuracy. 


When  two  axes  lie  in  different  planes,  motion  may  be  and  often  is  transmitted  from  one  to  the 
other  by  means  of  two  pairs  of  bevel-wheels ;  a  third  axis  being  introduced,  cutting  the  other  two. 
But  it  is  possible  to  make  a  pair  of  wheels,  one  upon  each  shaft,  whose  teeth  shall  be  composed  of 
rectilinear  elements,  touch  each  other  in  a  right  line,  and  transmit  rotation  with  a  constant  velocity 
ratio  directly,  thus  dispensing  with  the  countershaft  and  one  pair  of  bevel-wheels.  It  is  usually  the 
case  that  the  positions  of  the  axes  and  also  the  velocity  ratio  are  fixed  by  the  requirements  of  the 
mechanism  in  which  the  wheels  are  to  be  used. 

In  Fig.  2119,  let  A  B  represent  one  axis,  supposed  to  be  vertical  and  parallel  to  the  paper;  let 
CD,  also  parallel  to  the  paper,  represent  the  other  axis.  These  projections  intersect  at  E,  which 
point  represents  the  common  perpendicular  of  the  axes ;  this  line,  being  horizontal,  will  be  seen  in 
its  true  length  E'  A'  in  the  top  view  above,  where  A'  represents  the  vertical  and  C  D'  the  inclined 
axis.  The  lines  n  n,  m  m  are  now  drawn  parallel  to  A  B  and  C  D,  at  distances  from  them  which 
are  to  each  other  in  the  inverse  ratio  of  the  given  angular  velocities ;  these  intersect  at  P,  and  P  E 
will  here,  as  in  the  case  of  bevel-wheels,  represent  in  this  view  the  common  element  of  the  pitch- 
surfaces,  which  will  also  be  parallel  to  the  paper.  Through  any  point  of  this  line,  as  G,  another 
line  EH  can  be  drawn  perpendicular  to  it,  and  so  as  to  cut  both  the  axes.  Its  vertical  projection 
^^T will  be  perpendicular  to  G  E,  because  the  latter  is  parallel  to  the  paper;  in  the  horizontal  pro- 
jection, E,  being  a  point  in  the  vertical  axis,  will  appear  as  A',  and  H  will  appear  as  H'  in  C  D', 
thus  giving  A'  H  as  the  horizontal  projection  of  EH.  Now  project  G  to  G\  draw  G'  I'  parallel 
to  C  D',  and  it  will  be  the  horizontal  projection  of  G  E.     This  line  lies  in  a  plane  parallel  to  both 



axes,  and  intersects  at  /',  their  common  perpendicular,  dividing  it  into  segments  proportional  to 
A'  G',  G'  H',  and  therefore  to  EG,  G H:  by  revolving  around  A  B  it  will  generate  one  surface, 
and  by  revolving  around  C  D  it  will  generate  another,  tangent  to  the  first,  which  will  be  the  pitch- 
surfaces  of  the  wheels. 



These  surfaces  are  readily  constructed,  as  in  Fig.  2120,  where  the  inclined  line  A  B  revolves  about 
the  vertical  axis,  its  hast  distance  from  which  is  C  E.  Each  point  in  revolving  describes  a  horizon- 
tal circle,  whose  radius  is  seen  in  its  true  length  in  the  top  view.  It  will  be  seen  that  the  same  sur- 
face will  be  generated  by  a  line  seen  as  D  F  in  the  front  view,  and  as  BA  in  the  top  view ;  for  1) 
and  A  describe  the  same  circle;  so  also  do  G  and  /;  and  the  same  is  true  of  any  two  points  in 
these  lines  which  lie  in  the  same  horizontal  plane. 

The  two  surfaces  generated  by  the  line  G  E  of  Fig.  2119  are  shown  in  position  in  Fig.  2121  ;  the 
generatrix  being  prolonged  to  L,  SO  that  the  end  planes  are  equidistant  from  the  gorge-circles,  as  the 
transverse  sections  through  E  are  called.  These  surfaces  are  called  hyperboloids  «»t  revolution,  as 
it  can  be  shown  that  the  meridian  section  of  each  (as  11  K L  of  Fig.  2120)  is  a  hyperbola.  Their 
action  consists  of  rolling,  with  however  a  sliding  in  the  direction  of  the  common  clement,  because 
the  two  circles  which  move  in  contact  have  not  a  common  tangent.  To  make  this  clear,  the  gorge- 
circles  of  the  two  pitch-surfaces  are  shown  in  Fig.  2119,  in  dotted  lines,  in  the  to))  view  ;  their 
common  point  is  /'  ,•  and  if  the  inclined  one  turn,  it  will  cause  the  vertical  surface  to  rotate,  the 
directional  relation  being  shown  by  the  arrows.  In  the  other  view  the  common  point  of  these  two 
circles  is  E ;  and  at  the  instant  the  linear  velocity  of  the  inclined  circumference  may  he  represented 
by  E M,  a  tangent  to  it,  of  any  length ;  at  the  same  instant  that  of  the  other  gorge-circle  must  be 
also  represented  byitfl  tangent  EN.  The  length  of  the  latter  is  determined  by  the  consideration 
that  no  motion  in  the  direction  EG  would  transmit  rotation,  which  is  effected  solely  by  the  com- 
ponent EO  of  the  supposed  motion  EM,  which  is  perpendicular  to  EG,  0  M  being  the  tangential 
or  sliding  component;  and  the  resultant  EN  most  have  the  same  normal  component.  Now  the 
angular  velocities  will  be  equal  to  the  linear  velocities  EM,  EX,  divided  by  the  radii  V  E ',  FA  ; 

and  recollecting  that 

Then  we  have 

A'       A'  G' 

=  ,  we  will  let 

I' E'       G'S'       GH 

v  =  angular  velocity  about  inclined  axis  CD, 
v  =  angular  velocity  about  vertical  axis  A  B. 


v  =  Fe- 


v  = 

/'  A' 

from  similar  triangles  MEN,  E  /•'  //,  = 

But  from  similar  triangles  E  G II,  E  G  R. 

and  from  similar  triangles  E  G  F,  E  G  S. 
EG       G  S      G  S 



I'  A' 

K  M       F  G 

=  —        x           ,   or, 
EN       GH'      ' 


■    GH 

E II      FG 

~  GH  X  EF' 

EH      EG 

GH      GR' 

/••  G      G  8 

E  F      EG' 

whence  -,  = 

GR      EG       GR' 

which  demonstrates  the  correctness  of  the  process  of  constructing  the  surfaces,  as  previously  described. 

In  practice  thin   sections  or  frusta  only  of  the  surfaces  are  used.     In  Fig.  2122  are  shown  three 

pairs,  either  or  all  of  which  may  be  used,  the  hyperboloids  being  the  same  as  in  Fig.  2121.     The 

gorge-circles  are  the  mid-planes  of  the  central  pair  ;  but  practically  the  wheels  will  work  better  the 
farther  they  are  from  the  gorge-planes,  as  the  transverse  obliquity  of  the  common  element  diminishes 



as  it  recedes  from  them.  For  the  least  distance  between  the  axes  is  a  constant,  and  at  an  infinite 
distance  from  their  common  perpendicular  the  effect  of  their  separation  becomes  imperceptible,  so 
that  the  wheels  will  not  differ  appreciably  from  common  bevel-wheels. 

These  wheels  are  now  to  be  furnished  with  teeth  ;  and  the  proper  surfaces  are  generated  in  a 
manner  exactly  analogous  to  that  employed  in  the  cases  of  spur  and  bevel  gearing.  That  is  to  say, 
a  describing  hyperboloid  is  used,  which,  moving  in  contact  with  both  pitch-surfaces,  will  sweep  out, 
as  the  rotation  progresses,  a  flank  for  one  and  a  face  for  the  other.  If  in  Fig.  2121  we  suppose  the 
inclined  hyperboloid  to  be  the  pitch-surface  of  a  wheel  intended  to  work  with  another  equal  and 
similar  to  itself,  then  the  vertical  one  may  be  considered  as  the  describing  surface,  which  by  rolling 
upon  the  other  in  external  contact,  as  there  shown,  will  generate  the  face-surface  for  its  tooth.  But 
if  we  consider  these,  as  we  have  hitherto  done,  to  be  the  pitch-surfaces,  from  which  it  is  required  to 
construct  the  teeth  for  either  of  the  pairs  of  wheels  shown  in  Fig.  2122,  then  the  first  step  is  to  de- 
termine the  describing  hyperboloid  ;  and  for  convenience,  this  should  be  such  as  to  roll  with  either 
pitch-surface  with  a  velocity  ratio  expressible  in  whole  numbers.  Now,  referring  to  Fig.  2121,  the 
angular  velocity  of  the  inclined  hyperboloid  is  to  that  of  the  vertical  one  as  G  S  is  to  G  ft.  Sup- 
posing then  that,  the  vertical  one  and  the  velocity  ratio  being  given,  it  had  been  required  to  find  the 
inclined  one,  we  should  have  proceeded  thus  :  Knowing  G  S  and  the  velocity  ratio,  we  find  the  value 
of  G  ft,  with  which  as  radius  describe  about  G  the  arc  o  o,  and  through  E  draw  CD  tangent  to  this 
arc,  thus  determining  the  vertical  projection  of  the  required  axis.  Through  G  draw  F  G  perpendic- 
ular to  h  G,  cutting  A  B  in  F  and  CD  in  H.  The  horizontal  projection  of  G  Exs  G'  I',  and  that 
of  F  is  A',  as  before  explained,  so  that  the  horizontal  projection  of  F  G  is  A'  G'  ;  produce  this 
indefinitely,  project  /Tup  to  it  in  H\  through  which  point  draw  C  D  parallel  to  G'  i",  and  it  will 
be  the  horizontal  projection  of  the  required  axis.  If  in  this  way  we  draw  the  new  or  describing 
hvperboloid  externally  tangent  to  the  vertical  pitch-surface,  it  will  be  internally  tangent  to  the  other, 
and  vice  versa.  In  the  case  of  external  tangency  the  axes  are  on  opposite  sides  of  the  common  ele- 
ment; but  the  case  of  internal  tangency,  in  which  they  arc  on  the  same  side,  may  be  directly  con- 
structed as  in  Fig.  2123 ;  which  differs  from  Fig.  2119  only  in  this,  that  the  other  tangent  through 
-E"  to  the  same  circle  o  o  is  taken  for  the  vertical  projection  of  the  required  axis. 


Having  in  this  manner  drawn  the  describing  hyperboloid,  we  have  next  to  find,  by  means  of  it,  the 
tooth-surfaces.  The  principle  of  the  method  of  "doing  this  is  illustrated  in  Fig.  2124.  The  pitch- 
surface  is  the  one  with  the  vertical  axis ;  the  large  circle  in  the  top  view  is  the  upper  base,  and  the 
ellipse  within  it  is  the  intersection  of  the  inclined  describing  hyperboloid  by  the  plane  of  that  base. 
Were  the  describing  surface  to  rotate  while  the  other  stood  still,  the  describing  line  (which  in  this 
case  is  the  element  of  tangency,  A'  B)  would  always  pierce  the  plane  in  some  point  of  that  ellipse. 
But  both  hyperboloids  turn,  and  the  velocity  ratio  is  known ;  let  then  the  smaller  one  rotate  till  the 
describing  line,  whose  point  of  penetration  at  starting  is  A,  pierces  the  plane  in  the  point  1.  The 
pitch-surface  will  meantime  have  turned  through  the  known  angled  CI',  and  the  curve  1-1'  will 
have  been  traced  on  the  plane  of  the  base.  So  "when  the  point  of  penetration  reaches  2,  the  radius 
C  A  will  be  at  C2',  and  the  curve  2-2'  will  have  been  traced,  and  so  on.  It  is  to  be  noted  that  if 
the  rotation  be  in  the  opposite  direction,  the  curve  will  be  different ;  showing  that  the  two  flanks  of 



the  same  tooth  arc  not  alike,  as  they  may  be  and  usually  are  in  spur  and  in  bevel  gearing.  By  a 
process  exactly  similar  wc  may  determine  the  trace  of  the  tooth-surface  outside  the  pitch-hypcr- 
boloid,  upon  the  same  plane,  using  a  describing  hyperboloid  externally  instead  of  internally  tangent; 
and  it  will  be  found  that  the  difference  between  the  two  faces  of  the  same  tooth  is  still  more  marked 
than  in  the  case  of  the  flanks.  These  tooth-surfaces  are  composed  of  tight  lines,  and,  as  in  bevel- 
gearing,  the  teeth  become  larger  as  they  are  extended  in  length  ;  but  they  do  not  converge  to  a  point, 
nor  yet  arc  all  the  elements  in  the  end  view  of  the  wheel  tangent  to  the  gorge-circle,  nor  to  any  other 
circle,  as  sometimes  stated:  the  tooth-surface  makes  a  definite  trace  on  the  gorge-plane,  which 
ought  to  be  determined  for  the  sake  of  insuring  accuracy  in  the  drawing,  if,  as  is  most  frequently 
the  case,  the  frusta  employed  are  at  some  distance  from  that  plane,  like  either  of  the  outer  pairs  in 
Fig.  2122.  If  the  central  pair  be  chosen,  it  will  suffice  to  determine  the  trace  of  the  tooth-surfaces 
on  each  of  the  end  planes  of  the  frusta  ;  and  the  curvature  of  the  meridian  section  being  greatest  at 
the  vertex  of  the  hyperbola,  it  sh«uld  be  carefully  constructed  and  followed. 

But  if  the  frusta  be  remote  from  the  gorge-plane,  the  teeth  will  project  from  a  frustum  limited 
by  transverse  planes,  in  a  very  unsightly  manner.  The  fashioning  of  the  wheel  in  that  ease  is  illus- 
trated in  Tig.  2125.  Let  A  B  he  the  axis,  ED  the  generatrix,  of  the  hyperboloid,  of  which  EF\& 
the  radius  of  the  gorge,  and  FQ  a  part  of  the  meridian  section;  and  let  //  (V,  hi  lie  the  planes 
limiting  the  frustum  chosen.  The  curvature  of  the  hyperbola  diminishes  BO  rapidly  as  it  recedes  from 
the  vertex,  thai  in  many  eases  the  are  Q  /will  not  differ  sensibly  from  a  right  line.  If  then  at  P, 
the  middle  point  of  (I  1,  we  draw  a  tangent  to  the  curve,  cutting  A  I!  in  0,  it  will  in  revolving  de- 
scribe a  cone  0  C II  tangent  to  and  practically  identical  with  the  pitch-surface  within  the  assigned 
limits.  The  tangent  may  be  drawn  in  this  way:  AN  is  the  companion  generatrix  (see  Fig.  2120), 
and  like  ED  i>  an  asymptote  to  thi'  hyperbola.  Draw  through  I'  a  parallel  to  ED,  cutting  E  S  m 
L;  on  E S  make  L M '  =  E L,  and  J' M  will  lie  the  tangent  required.  Draw  a  /.',  /  I'  perpendicular 
to  PM;  these  will  be  the  elements  of  two  normal  cones,  by  which  the  wheel  is  limited,  as  in  the 
case  of  an  ordinary  bevel-wheel.  In  this  case  the  intersection  of  the  describing  hyperboloid  with 
the  outer  normal  cone  should  lie  firsl  found,  and  from  that,  by  a  process  analogous  to  those  of  Figs. 
2111  and  2121,  the  tooth-outline  on  that  cone  is  determined ;  and  by  a  similar  proceeding,  that  on 
the  inner  normal  cone.    The  parts  of  the  elements  of  the  teeth  intercepted  between  these  two  cones 

are  so  short  that,  as  before  remarked,  it  will  be  advisable  also  to  construct  the  trace  of  the  tooth- 
surface  on  the  gorge-plane  for  the  purpose  of  accurately  fixing  the  positions  of  these  elements.     The 

process  of  completing  the  drawings  of  the  wheel,  after  the  outline  of  a  tooth  on  each  normal  cone 
lias  been  found,  is  substantially  the  same  as  in  the  case  of  bevel-wheels.  Every  point  in  either  out- 
line moves  in  a  circle  around  the  axis  ;  these  circles  are  Been  as  BUCh  in  an  end  view,  and  as  right  lines 
in  the  side  view,  of  the  wheel.  The  tooth  is  therefore  first  drawn  in  the  end  view,  the  others  are 
copied  in  position,  and  the  points  in  the  various  circles  thence  projected  to  their  cure-]  onding  lines 
in  the  side  view. 

Now,  in  Fig.  2125,  it  will  be  observed  (hat  the  blank  for  the  wheel,  a  portion  of  which  is  shown  in 
outline  on  the  left,  is  composed  of  two  parts.     One  of  these  is  a  part  of  the  normal  cone  0 11 H, 

the  generatrix  R  II  being  extended  to  0, 
l26,  the  limit  of  the  projecting  part  or  face  of 

the  tooth.  The  other  is  a  portion  of  a  cone 
whose  vertex  is  not  C,  that  of  the  pitch- 
cone,  as  in  the  case  of  a  bevel-wheel,  but 
another  point  2V,  determined  as  follows : 
When  the  length  of  the  face  of  the  tooth 
has  been  decided  on,  the  describing  line 
will  have  a  known  position  with  relation  to 
the  axis  of  the  pitch-surface ;  and  by  re- 
volving around  the  latter,  it  will  generate 
another  hyperboloid.  The  meridian  sec- 
tion of  this  being  constructed,  a  definite 
arc  of  that  hyperbola  will  be  intercepted  be- 
tween R  0  and  V  IT,  which  like  0  1  will  be 
very  nearly  straight.  Bisect  this  arc,  and 
at  its  middle  point  draw  the  tangent  ON, 
which  will  generate  the  cone  required. 
This  is  necessary,  in  order  that  the  teeth 
may  begin  and  end  contact  all  along  an 
element :  if  it  be  not  done,  the  result  may 
be  that  they  will  begin  and  end  contact  at 
a  single  point,  which,  sustaining  all  the 
pressure,  will  be  rapidly  abraded. 

In  regard  to  the  division  of  the  pitch- 
circles,  the  state  of  things  at  first  sight  ap- 
pears quite  contradictory.  The  ratio  of 
the  radii  of  those  circles  which  move  in 
contact  is  not  the  same  as  the  velocity  ratio ; 
nor,  again,  is  the  ratio  between  the  radii  of 
any  two  pairs  of  circles  the  same.  Yet 
it  is  evident  that,  because  the  velocity  ratio  is  constant,  the  circles  must  be  divided  into  numbers  of 
parts  having  the  inverse  ratio  of  the  angular  velocities,  and  such  points  of  subdivision  will  come  into 
contact.     Ordinaiily,  as  shown  in  Fig.  2122,  two  pairs  of  these  wheels  may  be  used  on  the  same 



shafts,  equidistant  from  the  gorge-planes.  But  this  is  not  always  possible:  for  example,  in  Fig.  2126 
we  have  two  tangent  hyperboloids,  so  situated  that  the  projections  of  the  axes  on  a  plane  parallel  to 
both  intersect  at  right  angles.  This  case  presents  the  remarkable  feature  that  the  two  pitch-surfaces 
are  tangent  to  each  other  along  two  right  lines,  m  n,  r  s.  Now  from  these  surfaces  we  may  cut  the 
frusta  A,  B,  Fig.  2127,  tangent  along  mn;  and  at  the  same  time  we  can  make  use  of  the  smaller 
pair,  C,  D,  also  tangent  along  m  n  ;  the  arrows  indicating  the  relative  directions  of  the  rotations. 
Or,   as  in  Fig.   2128,   we  may  use  frusta 

which  are  tangent  along  the  other  genera-  2127. 

trix,  r  s ;  and  A  still  turning  in  the  same 
direction,  B  will  turn  in  the  opposite  direc- 

As  with  bevel-wheels,  then,  we  may  choose 
as  to  the  directional  relation  ;  but  evident- 
ly we  cannot  use,  as  in  Fig.  2122,  a  double 
pair  symmetrically  situated  in  reference  to 
the  gorge-planes.  It  will  practically  be  im- 
possible to  do  this,  even  before  reaching 
this  condition  of  double  tangency ;  for  the 



more  nearly  we  approach  it,  the  nearer  will  the  companion  generatrices,  and  therefore  the  surfaces, 
be  to  each  other  at  any  given  distance  from  the  element  of  tangency.  Consequently  the  teeth  will 
interfere  with  each  other  unless  one  pair  be  made  smaller  than  the  other,  even  when  the  axes  do  not 
have  exactly  the  relative  positions  here  supposed ;  but  the  smaller  and  more  numerous  the  teeth,  the 
more  nearly  may  this  limit  be  approached.  From  this  consideration  it  follows,  moreover,  that  the 
use  of  the  central  pair  of  wheels  shown  in  Fig.  2122  will  not  always  be  possible,  since  they  are  in 
fact  a  double  pair  of  frusta,  the  gorge-circle  in  each  hypurboloid  being  the  common  base  of  the  pair 
cut  from  it.  Nevertheless,  two  wheels  may  be  constructed,  and  furnished  with  teeth  which  will  work 
together  correctly,  without  interference,  the  blanks  being  disks  whose  mid-planes  are  the  gorge-circles 
of  Fig.  2126.  And  these  wheels  are  so  similar  in  appearance  to  that  which  would  be  presented  by 
one  of  the  class  now  under  consideration,  if  furnished  with  teeth  in  the  direction  of  one  of  the  gen- 
eratrices, that  it  has  been  stated  that  they  belong  to  this  class.  This,  however,  is  not  the  case,  as 
may  be  more  clearly  seen  from  the  fact  that,  if  the  central  frusta  can  be  used  at  all,  there  is  no  limit 
to  their  thickness,  or  properly  speaking  their  length,  as  measured  on  the  axes  ;  the  absurdity  of  which 
is  evident  from  a  glance  at  Fig.  2126.  The  wheels  mentioned  really  belong  to  the  next  class  of  gear- 
ing; the- teeth  are  composed  of  helical  instead  of  rectilinear  elements,  and  are  constructed  upon 
principles  and  in  a  manner  totally  different  from  the  foregoing. 


If  the  nut  of  a  common  screw  be  split  lengthwise  through  the  axis,  the  form  of  the  section  will 
be  that  of  a  rack  fitting  between  the  threads  of  the  screw ;  and  if  the  latter  be  turned,  the  rack  will 
be  driven  endlong,  as  though  it  were  a  complete  nut.  If  the  rack  is  of  sensible  thickness,  its  teeth 
may  be  just  such  as  would  be  obtained  by  splitting  out  of  the  nut  a  piece  of  the  assumed  thickness. 
The  outline  of  the  screw-thread  is  of  no  consequence  ;  every  point  in  it  describes  a  helix,  and  since 
this  is  equally  true  of  the  nut,  the  male  and  female  screws  are  superficially  identical,  and  there  is 
absolute  contact  over  so  much  of  the  surfaces  as  we  choose  to  employ.  Now  the  rectilinear  motion 
of  the  rack  may  be  regarded  as  a  rotation  about  an  infinitely  remote  centre.  If  this  centre  be 
brought  nearer,  the  rectilinear  path  of  any  point  will  become  a  circle  of  sensible  curvature.  Let  us 
then  first  consider  this  as  the  pitch-circle  of  a  spur-wheel,  and  construct  a  rack  which  shall  gear  with 
it.  Then  let  us  make  the  rack-tooth  the  outline  of  a  screw-thread,  the  axis  lying  in  the  plane  of  the 
pitch-circle.  If  the  screw  thus  formed  be  rotated,  it  will  drive  the  wheel  exactly  as  if  the  rack  were 
moved  endlong ;  because  all  the  meridian  sections  of  the  screw  are  alike,  and  by  construction  the 
rack-tooth  advances  in  the  direction  of  the  axis  at  a  rate  proportional  to  its  angular  velocity. 

This  is  illustrated  in  Fig.  2129,  by  consideration  of  which  it  will  be  seen  that  the  distance  of  the 
axis  of  the  screw  from  the  pitch-line  of  the  rack  is  arbitrary ;  that  is  to  say,  the  diameter  of  the 
screw  may  be  varied  without  affecting  the  velocity  ratio,  which  depends  upon  its  pitch.  This  in  the 
figure  is  the  same  as  that  of  the  teeth  of  the  rack,  forming  a  single-threaded  screw,  one  turn  of 
which  rotates  the  wheel  through  an  angle  measured  by  the  pitch  of  its  teeth ;  and  the  screw  may  be 
right-  or  left-handed,  according  to  the  directional  relation  desired.  We  may  dnible  the  pitch,  form- 
ing a  two-threaded  screw  and  doubling  the  angular  velocity  of  the  wheel ;  and  so  we  may  increase 
the  pitch  and  the  number  of  threads  to  any  desired  extent,  observing  that  the  pitch  of  the  screw 



must  be  a  whole  number  of  times  that  of  the  wheel-teeth,  and  its  diameter  such  as  to  avoid  too  great 
obliquity  of  action. 

We  have  thus  far  supposed  the  wheel  to  be  merely  a  thin  sheet,  or  plane.  In  giving  this  sensible 
thickness,  the  elements  of  the  teeth  cannot  be  made  parallel  to  the  axis,  as  in  a  spur-wheel,  but  must 
have  an  inclination  or  rather  twist,  depending  on  the  obliquity  of  the  threads  of  the  screw.  One 
mode  (if  determining  this  is  as  follows  :  Obviously  the  pitch-surface  of  the  wheel  is  a  cylinder,  and 
that  of  the  screw  is  another,  generated  by  the  revolution  of  the  pitch-line  of  the  rack  about  its  axis  ; 
and  the  two  are  tanpent  at  a  point.  If  now  the  helix  on  the  latter  be  developed  on  the  common 
tangent  plane,  and  then  wrapped  upon  the  pitch-cylinder  of  the  wheel,  it  "ill  become  another  helix. 
If  the  outline  of  the  wheel-tooth  lie  moved  along  this  helix,  parallel  to  itself,  we  shall  have  a  twisted 
tooth-surface,  precisely  like  that  of  Ilookc's  gearing.  It  will  work  correctly  with  the  screw,  to  whoso 
surface  it  is  tangent  at  a  point  only.  If  the  number  of  threads  of  the  screw,  and  also  its  diameter, 
be  sufficiently  increased,  it  may  be  made  to  have  the  appearance  of  another  wheel ;  and  if  the  diame- 
ters of  the  wheel  and  screw  in  this  way  he  made  equal,  they  will  so  closely  resemble  each  other  that 
this  combination  has  been  called  a  modification  of  Ilookc's  gearing.  Erroneously,  however;  for  not 
only  are  the  axes  here  in  different  planes,  not  only  may  the  velocity  ratio  be  varied  without  changing 
the  diameter  of  either  pitch-circle,  but  the  absolute  forms  of  the  teeth  of  the  two  wheels  arc  differ- 
ent, and  must  be,  in  order  to  transmit  the  rotation  with  a  perfectly  constant  velocity  ratio  by  the 
Bcrew-like  action,  which  in  this  case  is  the  effective  means.  For  instance,  the  wheel  shown  in  Figs. 
2129  and  2131  has  teeth  of  the  involute  form,  the  meridian  section  of  the  screw  being  therefore  a 
rack  with  sloping  teeth,  and  the  screw-  itself  a  true  oblique  helicoid ;  and  such  a  helieoid  it  will 
always  be,  whatever  the  diameter  or  number  of  threads:  the  outlines  of  these  threads  or  teeth  in 
all  its  transverse  sections  will  conseqiu  ntly  be  Archimedean  spirals,  and  not  involutes.  While  there- 
fore it  may  be  that  two  wheels  of  Ilookc's  form,  both  having  involute  teeth,  will  work  together  by 


the  screw-like  action  if  placed  in  gear  with  the  axes  in  different  planes,  the  fact  remains  that  the 
velocity  ratio  will  not  be  truly  constant.  In  all  screw-gearing  proper,  it  must  be  kept  in  mind,  the 
screw  or  worm,  whatever  its  size  or  the  number  of  its  threads,  is  a  rack,  which  virtually  advances  by 


rotation,  and  must  be  capable  of  driving  the  wheel  with  a  constant  velocity  ratio  if  it  be  bodily  moved 

But,  though  the  velocity  ratio  is  dependent  upon  the  number  of  threads  given  to  the  screw,  and  not 
upon  its  diameter,  yet  it  is  clear  that  for  any  given  pair  of  axes  and  velocity  ratio  there  must  be  some 
definite  ratio  between  the  diameters  of  the  screw  and  the  wheel,  involving  less  sliding  than  any 
other ;  and  this  may  be  found  as  follows :  In  Fig.  2130,  C  D,  A  B  are  the  axes,  A  E  their  common 
perpendicular.  We  first  proceed  exactly  as  in  Fig.  2119  to  find  the  line  seen  in  the  front  view  as 
E  G,  in  the  top  view  as  /'  67'.  This  line  would,  by  revolving  around  the  axes,  generate  two  hyperbo- 
loids,  which  would  work  together  with  the  given  velocity  ratio,  with  no  sliding  other  than  that  in  the 
direction  of  the  common  element.  The  radii  of  the  gorge-circles  would  be  A'  I',  I'  E :  taking  these 
gorge-circles  as  the  bases  of  the  pitch-cylinders,  we  have  the  required  proportions  for  the  diameters 
of  the  proposed  screw  and  wheel.  For  if  the  supposed  hyperboloids  were  given  angular  velocities 
having  any  other  than  the  assumed  ratio,  there  would  obviously  be  a  certain  amount  of  sliding  be- 
tween the  surfaces,  in  addition  to  that  in  the  direction  of  the  common  element ;  and  these  cylinders 
being  tangent  to  those  hyperboloids  at  the  gorge-circles,  the  same  is  true  of  them.  Furthermore, 
E  G  in  the  front  view  is  the  development,  upon  the  common  tangent  plane  of  these  cylinders,  of  the 
elementary  tooth,  or  helix,  upon  each  surface ;  and  it  will  be  observed  that  the  helices  formed  by 
wrapping  it  upon  the  cylinders  are  both  right-handed,  the  consequent  directional  relation  of  the  rota- 
tions being  indicated  by  the  arrows.  By  making  both  helices  left-handed,  this  relation  will  be 
reversed  ;  and  this  again,  it  will  be  seen,  is  consistent  with  the  derivation  of  the  cylinders  from  the 
hyperboloids,  since,  as  has  been  shown,  under  the  conditions  here  assumed  the  latter  will  be  tangent 
along  the  companion  generatrix  X Z,  which  being  wrapped  upon  the  cylinders  will  give  us  the  left- 
handed  helical  element,  so  that  the  directional  relation  is  optional. 

As  above  stated,  the  tooth-surface  of  a  wheel,  all  of  whose  transverse  sections  arc  alike,  will  be 
tangent  to  the  surface  of  the  screw  at  only  one  point ;  so  that,  though  strength  is  secured  by  giving 
the  wheel  definite  thickness,  yet  the  action  is  confined  to  the  single  plane  passing  through  the  axis  of 
the  screw.  But  line-co)dact,  instead  of  mere  point  contact,  can  be  secured  between  the  thread  of  the 
screw  and  the  wheel-tooth,  by  constructing  the  latter  as  shown  in  Fig.  2131.  The  meridian  section 
of  the  screw  is  determined  as  before,  that  is,  by  making  it  a  rack,  to  gear  with  a  wheel  whose  diame- 
ter is  that  of  the  pitch-circle  given,  as  shown  on  the  left ;  the  rack-tooth  being  straight  and  sloping, 
the  wheel-teeth  are  involutes  in  this  section,  which  is  the  one  made  by  the  plane  A  B.  From  this 
the  screw  being  constructed,  let  it  be  cut  by  any  other  plane,  as  L  0,  parallel  to  A  B.  This  section 
is  of  the  form  shown  on  the  right,  in  the  siJe  view  of  the  screw ;  and  it  may  be  considered  as  a 
rack-tooth  also.  It  was  shown  in  treating  of  spur-gearing  that,  in  the  case  of  two  wheels,  if  the 
tooth-outline  of  one  be  given  the  other  may  be  found  ;  and  by  an  analogous  process  we  can  ascertain 
the  form  of  the  wheel-tooth  which  shall  work  correctly  with  this  section  of  the  screw  as  a  rack-tooth. 
Any  number  of  other  parallel  planes  may  be  passed,  each  giving  a  different  rack-tooth  and  therefore 
requiring  a  different  form  to  be  given  to  the  wheel-tooth.  We  have,  then,  a  wheel  whose  transverse 
sections  are  not  alike,  but  vary  with  their  distance  from  the  axis  of  the  screw.  Each  one,  however, 
having  its  own  point  of  contact  with  the  screw-surface,  the  result  is  a  line  of  contact  between  the 
screw-thread  and  the  wheel-tooth,  which  line  will  partake  more  or  less  of  the  helical  form.  It  is 
usual  to  complete  the  shaping  of  the  wheel-blank  by  turning  off  its  corners,  as  the  sharp  project- 
ing points  of  the  teeth  would  be  weak  and  comparatively  useless ;  so  that  it  is  in  effect  terminated 
by  cones,  as  the  one  whose  element  is  C  V  in  the  figure.  In  making  the  drawing,  it  will  be  seen 
that  any  of  the  parallel  planes  used  in  the  construction,  as  R  S,  cuts  the  cone,  if  at  all,  in  a  circle ; 
and  when  the  wheel-tooth  to  work  with  the  corresponding  rack-tooth  cut  from  the  screw  by  the  same 
plane  has  been  drawn,  its  outlines  will  cut  this  circle  in  points  of  the  visible  contour  of  the  tooth. 
In  like  manner  all  other  points  in  that  contour  may  be  found,  since  every  transverse  section  of  the 
wheel-blank  is  circular,  whether  it  be  beyond  the  limit  of  that  conical  frustum  or  not,  as  for  instance 
that  by  the  plane  L  0. 

The  accurate  delineation  of  such  a  wheel  is  undeniably  tedious ;  but  the  making  of  the  wheel 
itself  is  accomplished  in  a  very  simple  way.  A  steel  screw  is  first  formed,  and  made  into  a  cutter 
by  providing  it  with  proper  notches  ;  it  is  then  set  to  cut  the  blank,  the  spaces  between  the  teeth  of 
which  are  first  "  roughed  out "  with  an  ordinary  cutter.  It  will  be  seen  that  when  the  cutting  is 
finished,  the  result  cannot  be  other  than  the  wheel  above  described.  For  the  cutter,  being  of  the 
form  of  the  screw,  must  drive  the  blank  correctly ;  it  must  cut  away  enough  metal  to  pass,  and,  as  it 
cannot  cut  outside  of  itself,  it  can  remove  no  more.  Every  section  of  the  screw  by  a  plane  parallel  to 
and  at  a  given  distance  from  the  axis  is  the  same ;  consequently  in  every  plane  of  the  wheel  paral- 
lel to  A  B  there  must  by  this  operation  be  formed  a  wheel-tooth  which  gears  correctly  with  the  sec- 
tion of  the  screw  by  that  plane,  considered  as  a  rack-tooth  advancing  by  rotation.  In  practice,  it  is 
necessary  to  take  more  than  one  cut,  and  after  each  cut  to  put  the  axes  of  the  wheel  and  cutter 
nearer  to  each  other.  The  outlines  of  the  elementary  rack-teeth  and  the  corresponding  wheel-teeth, 
then,  should  be  such  that  this  change  in  the  position  of  the  axes  does  not  affect  the  velocity  ratio  ; 
which  requires  that,  as  we  have  shown  them,  the  former  should  be  straight  and  sloping,  the  latter  of 
the  involute  form.  And  there  is  this  further  practical  advantage  in  this  fact,  that  the  cutter  and  the 
finished  screw  are  more  easily  made  in  this  way  than  in  any  other,  being  simply  oblique  helicoids,  or 
V-threaded  screws. 

Oblique  Screw-Gearing. — Thus  far  the  axis  of  the  screw  has  been  supposed  to  lie  in  a  plane 
perpendicular  to  that  of  the  wheel.  But,  though  this  is  the  case  most  frequently  met  with,  it  is  not 
at  all  essential  that  the  axes  should  be  thus  situated  ;  that  of  the  screw  may  cross  the  plane  of  rota- 
tion of  the  wheel  obliquely.  As  a  preliminary  to  the  construction  of  the  teeth  under  that  condition, 
it  is  to  be  noted  that,  though  a  rack  usually  moves  in  the  plane  of  rotation  of  its  wheel,  it  need  not 
do  so.     It  is  clear  that  a  rack  may  be  moved  in  a  direction  parallel  to  the  axis  of  the  wheel,  as  well 



as  at  right  angles  to  it ;  and  if  it  receive  both  motions  at  once,  the  rack  will  travel  obliquely  across 
the  plane  of  the  wheel,  still  working  with  a  constant  velocity  ratio,  as  will  be  seen  by  a  glance  at 
Fig.  2132.  Now  a  screw,  in  order  to  gear  obliquely  with  a  wheel,  must  act  in  a  manner  analogous 
to  that  of  the  rack,  as  is  shown  in  Fig.  2133.  A  B  is  the  axis  of  the  screw,  CD  that  of  the  wheel. 
In  the  top  view  we  have  shown  simply  the  pitch-cylinders,  with  an  elementary  helix  upon  that  of  the 
screw.  Let  us  now  suppose  a  thread  to  be  formed  upon  it,  and  cut  at  its  lowest  points,  a,  a',  by 
planes  perpendicular  to  the  axis  of  the  wheel.  These  sections  will  be  similar;  and  in  advancing 
from  the  position  a  to  the  position  «',  it  is  clear  that,  in  order  to  maintain  a  constant  velocity  ratio, 
this  section  of  the  thread  must  always  be  acting  against  a  section  of  the  wheel  by  a  plane  perpendic- 
ular to  its  axis ;  and  all  these  sections  must  be  alike,  as  shown  at  c,  e\  and  of  such  form  as  to  work 
with  a  considered  as  a  rack-tooth;  for  it  makes  no  difference  whether  a  be  moved  to  a'  by  bodily 
pushing  the  screw  in  the  direction  of  its  axis  or  by  turning  it. 

In  practically  laying  out  the  teeth  and  thread,  it  will  be  found  most  convenient  to  draw  the  pitch- 
cylinders  as  in  Fig.  2134,  the  elementary  helix  being  shown  as  passing  through  their  point  of  contact 
P.  Then  we  may  assume  the  form  of  the  section  of  the  screw-thread  by  LM,  the  mid-plane  of  the 
wTheel,  thus  forming  our  rack-tooth  ab,  and  determine  the  outline  of  the  wheel-tooth.  The  position 
of  every  point  in  the  outline  of  the  rack-tooth  with  respect  to  the  axis  of  the  screw  being  known, 
the  helices  described  by  these  points  may  lie  drawn  and  the  meridian  section  of  the  screw  ascertained. 
In  the  figure  it  will  be  observed  that  the  sides  of  the  rack-tooth  are  straight  and  sloping,  the  teeth 
of  the  wheel  being  therefore  involutes.  But  the  two  sides  of  the  rack-tooth  are  not  similarly  situa- 
ted in  relation  to  the  axis,  and  in  consequence  the  meridian  outline  of  the  screw-thread  will  not  be 
symmetrical,  nor  will  it  be  bounded  by  right  lines.  Nevertheless,  since  its  acting  sections  possess  the 
property,  before  mentioned,  of  admitting  a  change  in  the  distance  between  the  axes  without  affecting 
the  velocity  ratio,  it  is  necessary  that  the  screw  should  lie  formed  as  above  explained  if  it  is  re- 
quired to  cut  its  own  wheel  with  absolute  precision.     The  determination  of  its  form  involves  some 


labor;  but  a  converse  difficulty  of  equal  if  net  greater  magnitude  is  encountered  if  we  reverse  the 
process :  for  if  the  meridian  section  of  the  screw  be  assumed,  we  have  to  determine  the  form  of  a 
wheel-tooth  which  shall  work  with  an  oblique  section  of  the  thread  as  a  rack-tooth;  and  this  also 
will  result  in  a  non-symmetrical  outline,  the  fronts  and  backs  of  the  tooth  being  different,  if  the 
screw-thread  lie  symmetrical  in  the  first  place.  The  wheel,  then,  having  all  its  transverse  sections 
alike,  is  similar  to  one  of  those  used  in  Ilooke's  gearing,  its  teeth  having  a  twist  dependent  on  the 
obliquity  of  the  screw.  And  in  relation  to  this,  it  will  be  noted  that  the  pitch  of  the  screw  is  not, 
as  in  the  case  at  first  considered,  either  equal  to  or  necessarily  an  exact  multiple  of  that  of  the  wheel- 

The  elementary  helices  on  the  two  pitch-cylinders  must  evidently  coincide  when  developed  on  the 
common  tangent  plane ;  and  the  mode  of  determining  the  pitch  of  the  screw,  and  also  that  of  the 
wheel-helix,  when  the  pitch  of  the  wheel-teeth  is  given,  is  shown  in  Fig.  2135.  A  B  is  the  axis  of 
the  screw,  C  D  that  of  the  wheel,  P  the  point  of  contact  of  the  pitch-surfaces,  and  L  M  the  plane 
of  rotation  of  the  wheel,  all  as  in  Fig.  2134,  both  axes  and  the  common  tangent  plane  being  parallel 
to  the  paper.  Let  PFhe  the  developed  pitch  of  the  wheel-teeth  ;  then  make  P  K,  perpendicular  to 
A  B,  equal  to  the  circumference  of  the  pitch-cylinder  of  the  screw ;  draw  K  E,  produce  it  to  cut  A  B 
in  G,  and  P  G  is  the  pitch ;  the  screw  then  is  single-threaded,  one  rotation  advancing  the  wheel 
through  an  angle  measured  by  its  pitch.  If  it  be  desired  to  make  the  screw  two-threaded,  and  thus 
to  double  the  angular  velocity  of  the  wheel,  it  will  not  do  to  double  the  pitch  thus  found,  as  in  the 
case  of  the  ordinary  worm  and  wheel:  we  must  set  off  PF equal  to  twice  the  developed  pitch  of 
the  wheel-teeth,  draw  KF,  and  produce  it  to  cut  A  B  in  H,  giving  PH  &s  the  pitch  of  the  screw  ; 
and  so  on  if  any  other  angular  velocity  is  to  be  given  to  the  wheel.  The  lines  corresponding  to  PIf, 
G  K  are  drawn  in  Fig.  2133,  which  will  make  the  application  of  this  construction  clear :  a  line  N  0, 
drawn  through  P  parallel  to  G  K,  as  shown  also  in  Fig.  2134,  is  evidently  the  development  and  com- 
mon tangent  of  the  elementary  helices  on  both  pitch-cylinders  which  pass  through  their  point  of 

The  construction  explained  in  connection  with  Fig.  2130,  in  relation  to  the  ordinary  worm  and 
wheel,  is  also  true  in  the  case  of  oblique  screw-gearing.     That  is  to  say,  if  the  axes  and  velocity  ratio 



be  given,  the  screw  and  wheel  which  will  work  with  the  least  sliding  are  determined  by  first  construct- 
ing the  rolling  hyperboloids  which  satisfy  the  assigned  conditions,  and  then  taking  as  the  pitch-sur- 
faces the  cylinders  tangent  at  their  gorge-circles ;  the  common  element  of  the  hyperboloids  being 
also  taken  as  the  development  and  common  tangent  of  the  elementary  helices.  Those  hyperboloids 
in  this  case  having  but  one  line  of  tangency,  the  directional  relation  of  the  rotations  is  thereby  fixed  ; 
the  helix  of  the  screw  cannot  be  made  right-handed  or  left-handed  at  option,  as  in  Fig.  2130. 

Again,  it  was  seen  that  when  the  axis  of  the  screw  lies  in  the  plane  of  rotation  of  the  wheel,  both 
helices  must  be  either  right-handed  or  left-handed.  But  when  it  crosses  that  plane  obliquely,  it  will 
be  seen  from  Fig.  2136  that  this  is  not  always  the  case.  A  B,  C D,  L  M,  PA' being  the  same  as  in 
Fig.  2135,  let  P  E,  PF,  P  A  be  respectively  once,  twice,  and  thrice  the  developed  wheel-pitch ;  then 
P  G,  P  H,  P  S  are  the  pitches  of  a  single-,  a  double-,  and  a  treble-threaded  screw.  Recollecting 
that  G  K,  H  K,  and  S K  touch  the  screw-cylinder  on  its  lower  side,  it  will  be  seen  that  all  the  screw- 
helices  will  be  right-handed.  But  as  these  lines  touch  the  wheel-cylinder  on  its  upper  side,  it  will 
also  be  seen  that  when  S  K  is  wrapped  upon  that  cylinder  it  will  form  a  right-handed  helix,  while 
G  A"  will  form  a  left-handed  one.  The  proportions  in  this  illustrative  diagram  are  such  that  UK  is 
parallel  to  CD;  it  therefore  will  form  no  helix  at  all,  but  the  wheel  will  be  simply  a  common  spur- 
wheel,  the  elements  of  the  tooth-surfaces  being  parallel  to  the  axis. 

From  the  mode  of  generation,  it  is  clear  that  the  action  will  be  confined  to  the  plane  passing 
through  the  axis  of  the  screw  and  the  common  perpendicular  of  the  two  axes,  represented  by  A  B 
in  Figs.  2133,  2134,  and  2137,  each  section  of  the  screw-thread  by  that  plane,  on  the  side  which  is 
in  gear  with  the  wheel,  touching  the  tooth  of  the  latter  in  a  point  whose  distance  from  the  pitch- 



surfaces  is  determined  by  the  construction  of  the  rack  and  wheel  in  Fig.  2134.  Consequently  the 
greatest  length  of  the  screw,  as  in  the  ordinary  worm  and  wheel,  is  determined  by  the  distance 
through  which  the  teeth  of  the  elementary  rack  travel  while  actually  in  gear  with  those  of  the  wheel. 
This  being  ascertained  and  set  off  as  D  E  on  the  axis  A  B,  Fig.  2137,  the  screw-blank  is  terminated 
by  planes  through  D  and  E  perpendicular  to  A  B,  the  outer  cylinder  being  shown  in  full  lines,  and 
the  inner  one,  or  core  of  the  screw,  being  dotted. 

The  thickness  of  the  wheel  may  be  determined  thus-:  Through  D  and  A  pass  planes  G  H,  IK, 
perpendicular  to  the  axis  ;  these  may  limit  the  teeth  of  the  wheel  at  their  tops,  since  any  further 
extension  in  the  direction  of  the  axis  would  be  useless.  The  wheel-blank  need  not  be  cylindrical, 
but  may  have  the  form  shown,  which  is  thus  determined:  The  radius  PF,  obviously,  will  be  the 
distance  from  the  axis  of  the  wheel  to  the  outside  of  the  core  of  the  screw-blank,  measured  on  the 
common  perpendicular,  minus  whatever  may  be  allowed  for  clearance.  The  plane  G  D  H  cuts  that 
core  in  an  ellipse,  of  which  a  part  is  shown  in  section  in  the  front  view,  where  A'  B'  is  the  axis  of 
the  screw,  C  that  of  the  wheel,  whose  section  by  this  plane  is  the  circle  G'  H ,  which  must  evidently 
clear  the  elliptical  section.  And  by  a  like  proceeding  with  other  transverse  planes,  we  may  deter- 
mine as  many  points  as  are  necessary  in  the  curve  G  F I,  which  practically  may  be  made  a  circular 
arc.  Drawing  at  G  and  /lines  normal  to  this  curve,  the  wheel-blank  is  terminated,  as  in  Fig.  2137, 
by  short  conical  frusta.  The  tooth-surfaces  are,  of  course,  not  affected  by  this  departure  from  the 
cylindrical  outline,  their  transverse  sections  remaining  the  same ;  the  depths  of  the  teeth,  merely, 
increase  as  they  recede  from  the  mid-plane  L  M. 



Oblique  Screw  and  Rack. — Let  A,  Fig.  2138,  be  a  common  Y-thrcadcd  screw,  whose  axis  is  par- 
allel to  the  paper.  If  we  svippose  this  screw  to  be  moved,  without  rotating,  in  a  direction  perpen- 
dicular to  the  paper,  through  some  plastic  material,  the  result  would  be  the  formation  of  a  rack,  B, 
whose  teeth  are  composed  of  parallel  elements,  which  touch  the  screw  at  points  of  its  visible  con- 
tour. If  the  screw  now  remain  stationary,  but  free  to  rotate,  we  can  move  the  rack  perpendicularly 
to  the  paper  without  turning  the  screw,  or  it  mav  be  driven  endlong  by  the  rotation  of  the  screw,  or 
it  may  receive  both  motions  at  once.  In  the  latter  case  the  resultant  is  an  oblique  travel  of  the  rack 
across  the  plane  of  rotation,  as  in  Fig.  2132  ;  and  the  degree  of  obliquity  is  entirely  arbitrary,  so  long 
as  it  is  not  so  great  as  to  prevent  the  screw  from  driving  the  rack.  We  have  taken  the  V-threaded 
screw,  and  supposed  the  rack-teeth  to  be  perpendicular  to  the  paper,  only  for  the  sake  of  simplicity 
in  illustration.  Evidently  the  same  may  be  done  with  a  screw  of  any  reasonable  meridian  section, 
and  in  all  cases  there  is  a  line  of  contact  between  each  thread  of  the  BCrew  and  its  rack-tooth. 

But  again,  the  screw  need  not  be  moved  in  the  direction  above  supposed  in  generating  the  rack, 
nor  is  it  the  best  direction.  This  will  be  seen  from  Fig.  2189,  in  which  A  is  the  outer  cylinder  or 
blank  of  the  screw,  upon  which  the  helix  is  Bhown;  Sis  that  plane  section  of  the  rack  which  is 
parallel  to  the  elements  of  its  own  teeth  and  tangent  to  the  cylinder  A.  Now  let  us  suppose  that 
the  rack  is  to  be  driven  by  the  screw  as  indicated  by  the  arrows.  Then,  if  the  screw  be  formed  into 
a  cutter,  the  spaces  in  the  rack  being  "roughed  out"  as  usual,  it  is  clear  that  the  rack  will  be  driven 
by  the  cutter  as  it  works,  and  in  one  revolution  it  will  be  driven  just  far  enough  for  the  cutter  to 
clear  itself.  In  doing  this,  it  is  also  clear  that  the  helix  shown,  its  point  of  contact  advancing  in  one 
turn  from  P  to  O,  must,  in  order  to  remove  the  least  metal,  trace  upon  the  plane  B  a  line  which  will 
be  always  tangent  to  the  In  li\.  Draw,  then,  P K perpendicular  to  C D  and  equal  to  the  circumfer- 
ence of  the  cylinder,  and  6  K  will  be  the  direction  of  the  teeth  of  the  rack,  which  latter  w  ill  travel 
through  the  distance  P  Eat  each  revolution  of  the  screw.  The  form  then  of  the  rack-teeth  will  be 
determined  by  simply  making  a  drawing  of  the  screw  as  seen  from  the  direction  K  G,  the  outlines 
of  their  normal  sections  being  those  of  the  visible  spaces  between  the  adjacent  threads  and  all  the 
elements  necessarily  parallel  to  <1  A".  If  the  size  of  the  screw-blank,  and  the  pitch  P  K  of  the  rack 
in  the  direction  of  its  travel,  be  given,  we  may  by  a  converse  operation  determine  the  pitch  of  the 
screw.  Drawing  P  K as  before,  Bet  off  PE;  then  draw  K  K  and  produce  it  to  cut  C  I)  in  G,  thus 
giving  /'  ff,  the  required  pitch. 


This  form  of  gearing  was  formerly  much  used  in  wooden  mill-work,  but  i-  now  seldom  met  with 
in  heavy  machinery,  bevel-gearing  being  used  instead.  The  latter  has  the  advantage  that  the  teeth 
are  in  contact  along  a  line,  thus  distributing  the  pressure  and  the  wear  over  a  considerable  surface 
during  the  action  ;  whereas  in  the  former  the  teeth  touch  each  other  in  a  single  point  only,  so  that 
during  the  whole  action  the  wear  is  confined  to  a  mere  line  joining  the  BUCCessive  points  of  tangency. 
Yet  in  light  mechanism  the  facility  of  forming  the  teeth  in  the  lathe  may  make  it  desirable  to  employ 
this  form  of  gearing.  The  name  is  derived  from  the  fact  that  the  turned  pins  forming  the  teeth  are 
often  set  in  the  faces  of  circular  disks,  as  in  Fig.   2140.     In  this  case  the  teeth  are  cylindrical  pins, 



and   the  two  wheels   are  exactly  alike  in 
every  particular.     The  axes  are  not  in  the 
same  plane,  but  situated  like  those  of  the 
common  worm  and  'wheel;  that  is  to  say, 
their  projections  upon  a  plane  parallel  to 
both  intersect  at  right  angles,  and  the  length 
of  their  common  perpendicular  is  equal  to 
the  diameter  of  the  pins.     Under  these  cir- 
cumstances it  is  clear  that  the  angle  D  C  E  will  always  be  equal  to  the 
angle  I G  H,  so  long  as  the  pin  E  of  the  wheel  A  is  in  contact  with  the 
pin  H  of  the  wheel  B.     The  velocity  ratio  is  therefore  perfectly  constant. 
It  will  be  noted  that,  the  arrows  indicating  the  directions  of  the  rotations,  ' 

the  length  of  the  pin  E  must  be  such  that  the  next  pin  F  of  the  other 

wheel  B  shall  not  catch  upon  its  end  in  going  into  gear.  And  it  will  also  be  seen  that,  although 
at  the  instant  of  coming  into  contact  with  the  next  pin  0  of  the  driver  A,  the  pin  i^may  also  touch 
the  pin  E  on  the  back,  it  eannot  continue  to  do  so.  That  is  to  say,  it  is  not  possible  even  theoret- 
ically to  secure  entire  freedom  from  backlash. 



The  maximum  length  of  one  pin  having  been  determined,  it  is  of  course  the  same  for  all ;  and  it 
is  next  to  be  observed,  that  if  the  number  be  increased,  this  length  must  be  diminished ;  also,  that  in 
every  case  there  will  be  a  limit  beyond  which  the  number  cannot  be  increased  without  also  diminish- 
ing the  diameter,  and  in  consequence  the  distance  between  the  axes.  It  therefore  follows  that  ulti- 
mately the  axes  will  intersect  at  right  angles,  and  the  pins  will  become  consecutive  points  in  the  cir- 
cumferences of  two  equal  circles  rolling  together  like  the  bases  of  the  pitch-cones  of  a  pair  of 
mitre-wheels.  In  other  words,  as  stated  in  the  synopsis  at  the  beginning  of  this  article,  there  are  no 
pitch  surfaces,  these  degenerating  into  lines,  and  the  elementary  teeth  into  points.  But  if  we  suppose 
the  axes  to  intersect  at  right  angles,  cylindrical  pins  may  yet  be  used  on  one  wheel,  and  a  constant 
velocity  ratio  maintained  by  making  the  teeth  of  the  other  in  the  form  of  surfaces  of  revolution,  if 
the  meridian  outline  of  the  latter  bo  correctly  determined.  The  manner  in  which  this  outline  is  to 
be  ascertained  will  be  understood  by  the  aid  of  Fig.  2141,  where  the  two  wheels,  A  and  B,  are  of 
the  same  diameter.  Let  a  be  a  pin  of  no  sensible  diameter  in  the  wheel  A,  and  c  another  in  the 
wheel  B,  the  distance  a  c  between  them  being  arbitrary.  Let  the  wheels  now  turn  as  shown  by  the 
arrows,  with  a  constant  velocity  ratio ;  then,  when  a  reaches  e,  c  will  have  gone  to  g,  the  arcs  a  e 
and  eg  being  equal.  The  distance  between  the  pins  in  the  two  wheels  is  now  changed  ;  eg  is  greater 
than  a  c,  and  it  is  also  lower,  that  is,  nearer  to  the  face  of  B.  The  relative  positions  of  the  pins  may 
in  a  similar  manner  be  obtained  in  any  number  of  intermediate  positions ;  and  it  will  be  seen  that  if 
the  vertical  line  c  be  taken  as  the  axis  of  a  surface  of  revolution,  the  radii  of  whose  sections  are  the 
perpendiculars  from  a  upon  c  in  those  intermediate  positions,  we  shall  have  the  form  of  a  pin  or 
tooth  for  B,  such  that  it  will  be  driven  by  a  pin  in  A,  of  no  sensible  diameter,  from  c  to  g  with  a 
constant  velocity  ratio.  If  we  now  suppose  a  to  move  from  e  to  b,  this  tooth  will  be  driven  from  g 
to  d  ;  and  by  repeating  the  above  process  we  may  find  the  meridian  outline  required  to  maintain  a 
constant  velocity  ratio  during  that  part  of  the  action. 

This  process  is  illustrated  more  fully  in  Fig.  2142,  in  which  only  the  pitch-circles  arc  shown,  and 
for  convenience  these  are  made  tangent  at  e.  When  the  pin  a  occupies  the  positions  1,  2,  the  axis 
c  will  be  at  1,2';  by  the  aid  of  which,  as  above  explained,  the  outline  ax  is  obtained,  as  that  of  a 



tooth  which  will  be  correctly  driven  by  a  through  the  arc  c  g',  which  is  equal  to  a  e.  In  going  from 
e  to  b,  the  pin  must  drive  the  tooth  to  d  ;  and  that  the  velocity  ratio  may  be  constant,  the  outline 
must  be  that  of  the  curve  b  z. 

It  will  be  observed  that,  the  points  a,  b  being  projected  to  a',  b'  upon  the  circle  B  B,  which  is 
equal  to  A  A,  we  have  the  equal  arcs  a  c ,  b'  d',  subtending  equal  angles  at  the  centre  of  B  B,  the 
radii  of  the  upper  bases  of  the  teeth  on  the  left  and  right  hands  respectively  being  therefore  equal 
to  a'  o,  b' p.  Now,  in  Fig.  2143,  let  C  be  the  centre  of  the  circle  B  B,  and  let  a',  c',  and  o  corre- 
spond to  the  points  similarly  lettered  in  Fig.  2142.  Let  de  be  a  chord  equal  to  a  c',  but  nearer  to 
the  vertical  line  C  T,  to  which  c  b,  e  h  are  parallel,  and  draw  dg  perpendicular  to  e  h.  Then,  in  the 
triangles  b  a  c,  h  d e,  we  have  the  angle  at  a'  equal  to  the  angle  at  (/,  also  a  c'  —  de,  but  the  angle  at 
h  less  than  the  angle  at  b.  Consequently  d  g  is  greater  than  a'  o  ;  that  is  to  say,  referring  to  Fig. 
2142,  the  radius  of  the  tooth  will  increase  from  a  toward  x,  the  maximum  being  reached  when  a'  c' 
has  the  position  i  k  in  Fig.  2143,  being  then  bisected  by  the  plane  of  the  axes.  And  in  a  similar 
manner  it  may  be  shown  that  during  the  receding  action  the  radius  of  the  tooth  will  diminish  as  it 
recedes  from  the  plane  of  centres,  or  in  other  words  from  z  toward  b  in  Fig.  2142 ;  as  will  be  seen 
by  comparing  the  triangles  Imp,  rtu,  in  which  I m  =  r  t,  the  angle  at  r  is  equal  to  the  angle  at  /, 
but  the  angle  at  p  is  less  than  the  angle  at  u,  whence  In  is  greater  than  rs.  Now,  in  Fig.  2143,  let 
a'  and  r  be  equidistant  from  T :  then  in  the  triangles  b  a  c' ,  rtu,  we  have  a'  c!  =  rt ;  also  tur 
=  u  CT=a'  be'.  But  ba  c',  which  is  equal  to  Crt,  is  less  than  90°,  whence  tru  is  greater 
than  90°.  Therefore  a  o  is  greater  than  r  s  ;  and  the  same  being  true  for  other  points  equidistant 
from  T,  it  follows  than  in  Fig.  2142  all  the  radii  of  the  tooth  a  z,  except  the  lowest  one,  are  greater 
than  those  of  the  tooth  b  z.  The  consequence  of  this  is  that,  since  the  teeth  are  to  be  turned  in  the 
lathe,  the  smaller  outline  must  be  selected ;  and  in  order  to  secure  receding  instead  of  approaching 
action,  the  cylindrical  pins  must  be  given  to  the  driver,  and  those  of  the  form  above  discussed  to 
the  follower.  In  giving  sensible  diameter  to  the  former,  a  change  is  of  course  made  in  the  elemen- 
tary form  of  the  latter.  A  process  is  here  pursued  analogous  to  that  employed  in  the  case  of  the 
pin-wheels  described  in  the  section  on  spur-gearing;  that  is,  a  series  of  circular  arcs  are  described 
whose  centres  are  in  the  elementary  outline  b  z,  with  the  radius  assumed  as  that  of  the  pin ;  the 
curve  tangent  to  those  arcs  is  the  meridian  outline  of  the  actual  tooth. 



But  it  is  not  necessary  that  the  diameters  of  the  pitch-circles  shall  be  equal.  In  Fig.  2144,  B  B 
is  the  larger,  the  cylindrical  pins  being  given  to  A  A,  whose  centre  is  C.  The  mode  of  constructing 
the  curves  ax,  bz  is  precisely  the  same  as  in  Fig.  2142;  and  the  lettering  of  the  two  figures  being 
made  as  far  as  possible  to  correspond,  it  can  be  readily  traced,  the  arcs  ae,  eb  being  respectively 
equal  to  the  arcs  c  g,  g  d .  The  positions  of  the  points  a,  e,  b,  and  the  intermediate  ones,  on  the 
circle  A  A,  with  relation  to  the  assumed  axis  c  c  in  its  progress  to  dd! ,  are  evidently  precisely  the 
same  as  those  of  the  corresponding  points  on  the  equal  circle  A'  A',  whose  centre  is  c';  the  latter 
serving  better  to  point  out  the  peculiarities  due  to  the  change  in  the  relative  diameters  of  the  pitch- 
circles  A  A  and  B  B.  These  will  be  clear  by  the  aid  of  Fig.  2145,  in  which  D  is  the  centre  of  the 
circle  B  B,  C  that  of  the  circle  A'  A',  the  two  being  tangent  at  e.  Let  the  arcs  eo,  co!  be  equal, 
and  of  any  length  less  than  90°  on  either  circle ;  and  let  er,  eb'  be  respectively  equal  to  them, 
making  a'  mb',  onr  perpendicular  to  e  C  D.  Then,  because  the  arcs  e o,  e a'  arc  equal,  the  chord 
a  e  is  less  than  the  chord  o  e,  and  a'  m  is  less  than  o  n.  Therefore,  drawing  through  a'  a  parallel  to 
e  C  D,  it  will  cut  the  arc  oe  in  some  point  c'.  The  linear  velocities  of  the  circumferences  being 
equal,  when  a'  has  reached  e,  c  will  be  found  at  g,  eg  being  equal  to  o  c'  ;  and  when  a'  reaches  6', 
c  will  be  at  d',  r  d!  being  also  equal  to  o  c'.  Draw  through  d'  another  parallel  to  e  C  D,  and  pro- 
long a  b'  to  meet  it  in  p.  We  then  perceive  that,  whatever  the  lengths  of  the  arcs  eo,  c a',  the 
distance  a'  m  is  always  less  than  a  n,  and  the  longer  the  arcs  the  greater  this  difference,  which  is 
equal  to  that  between  n  r  and  m  b' ;  and  that  as  d  always  lies  beyond  r,  b'  p  will  always  be  greater 
than  this  difference.  Now,  if,  as  in  Fig.  2144,  we  assume  a  c'  as  the  axis  of  a  tooth  of  B  B,  to  work 
with  a  cylindrical  pin  at  a  in  A  A,  of  no  sensible  diameter,  that  tooth  will  be  pointed  as  shown,  the 
curve  a  x  being  suited  for  the  arc  of  approaching  action  a  e,  if  A  A  drive  as  shown  by  the  arrows, 



which  are  here  made  to  correspond  with  Fig.  2142.  The  tooth  b  z,  for  the  arc  of  receding  action, 
has  however  at  the  point  b  a  radius  equal  to  b'  p.  Since,  when  the  teeth  are  turned  in  the  lathe,  the 
smallest  must  be  used,  it  follows  that  under  these  conditions  the  curve  a  x  must  be  employed  in 
determining  the  meridian  outline  of  the  working  tooth,  and  that  in  order  to  secure  receding  instead 
of  approaching  action  the  cylindrical  pins  must  be  given  to  the  follower. 

If  the  diameter  of  BB  be  increased,  its  curvature  will  diminish,  and  at  the  limit  will  disappear, 
the  circle  becoming  the  tangent  to  A  A.  The  curves  a  x  and  b  z  will  then  evidently  be  equal  and 
similar,  each  being  the  cycloid  of  which  A  A  is  the  generating  circle ;  and  we  have  the  case  of  a 
rack  driving  a  pin-wheel.  There  is  in  fact  a  close  analogy  between  the  form  of  gearing  now  under 
consideration  and  that  already  described  as  pin-wheel  gearing ;  for  if  in  face-gearing  we  suppose  the 
axes  to  be  parallel,  the  teeth  will  be  turned  pins  placed  radially  in  the  convex  surface  of  a  cylinder, 
and  their  outlines  precisely  the  same  as  those  of  a  spur-wheel,  the  cylindrical  pins  being  the  same  in 
both  cases. 

When  the  cylindrical  pins  are  given  to  the  larger  of  two  wheels  whose  axes  meet  at  right  angles, 
as  in  Fig.  2146,  the  case,  as  will  be  seen  by  comparing  this  diagram  with  Fig.  2144,  is  nearly  the 
converse  of  the  previous  one.  The  rotations  being  still  in  the  same  direction,  the  pointed  tooth  ap- 
pears on  the  opposite  side  of  the  plane  of  the  axes,  and  the  cylindrical  pins  must  drive,  in  order  to 
secure  receding  action.  It  will  be  observed  that,  as  the  diameter  of  A  A  is  increased,  the  shorter 
will  the  teeth  of  BB  become  for  a  given  arc  of  action;  and  this  diameter  cannot  be  indefinitely  in- 
creased, since  at  the  limit  the  axes  of  the  cylindrical  pins  will  lie  in  the  plane  of  rotation  of  B  B. 
Still  the  pin-rack  may  be  made  to  work,  by  placing  the  pins  perpendicular  to  that  plane,  and  making 
the  axes  of  the  teeth  of  BB  radial,  the  outlines  being  involutes  of  the  pitch-circle;  but  in  that 
case  the  wheel  must  drive,  as  already  explained  in  treating  of  spur-gearing. 

A  process  similar  to  those  above  described  may  also  be  employed  when  the  axes  are  situated  as  in 



Figs.  2140  and  2141,  although  the  diameters  of  the  wheels  are  unequal,  and  the  forms  of  teeth  for 
one  ascertained  which  will  gear  correctly  with  cylindrical  pins  on  the  other ;  and  that  even  when  the 
common  perpendicular  of  the  axes  is  greater  than  the  diameter  of  the  pins.  But  neither  the  dis- 
tance between  the  axes  nor  the  difference  between  the  diameters  of  the  wheels  can  be  varied,  except 
within  quite  narrow  limits,  when  the  axes  thus  lie  in  different  planes. 

It  is  not  necessary,  however,  that  the  pins  or  teeth  of  gearing  of  this  form  should  be  inserted 
into  plane  surfaces ;  of  which  the  suggestion  above  made  in  regard  to  the  pin-rack  is  an  illustration, 

since  the  radial  teeth  of  the  driving  wheel  would  be  fixed  in  the  periphery  of  a  cylinder.  But  if, 
as  shown  in  Fig.  2147,  the  axes  intersect  at  any  angle,  we  may  proceed  as  follows:  Draw  E K, 
dividing  the  angle  A  ED  according  to  the  velocity  ratio  assigned,  precisely  as  in  bevel-gearing. 
Supposing  that  cylindrical  pins  are  to  be  given  to  the  wheel  with  the  vertical  axis,  draw  through 
any  point  E of  EK a  parallel  to  A  B,  as  the  axis  of  such  a  pin;  also  through  i^draw  EG  per- 
pendicular to  A  B,  and  produce  it  to  meet  the  other  axis  CD  in  the  point  /:  then  F I'm  revolving 
around  CD  will  generate  the  cone  E I L.  The 
teeth  of  the  inclined  wheel  are  to  be  solids  of  revo- 
lution, whose  axes  will  evidently  be  elements  of 
this  cone,  and  they  may  be  fixed  in  the  surface  of 
another  cone  X M  0,  normal  to  F I L.  A  pin  of 
the  vertical  wheel  is  shown  at  F  in  contact  with 
such  a  tooth,  of  which  the  form  may  be  thus  de- 
termined :  First  let  the  cylindrical  pin  be  supposed 
of  no  sensible  diameter;  then,  if  the  vertical  wheel 
be  turned  through  any  angle,  the  inclined  one  will 
be  driven  through  an  angle  which  is  known,  since 
the  circumferential  velocities  of  the  circles  whose 
radii  are  F  G,  FH  must  be  equal.  Consequently, 
the  relative  positions  of  the  axes  of  the  cylindrical 
pin  and  of  the  required  tooth  may  be  determined 
at  any  phase  of  the  action,  and  their  common  per- 
pendicular found.  Having  repeated  this  process  a 
sufficient  number  of  times,  these  common  perpen- 
diculars will  evidently  be  the  radii  of  the  transverse  sections  of  the  required  tooth  to  work  with  a 
pin  of  no  sensible  diameter,  from  which  the  meridian  section  may  be  constructed,  and  from  it  the 
outline  of  a  working  tooth  derived  in  the  usual  manner  by  assigning  any  diameter  at  pleasure  to  the 
cylindrical  pin. 

This  arrangement  may  also  be  modified  as  in  Fig.  2148,  the  cylindrical  pins  being  fixed  in  the 
periphery  of  a  cylinder,  from  which  they  project  radially ;  the  construction  of  the  tooth  of  the  other 
wheel  being  made  exactly  as  in  the  previous  case.     And  it  is  hardly  necessary  to  remark  that  in 



cither  modification  the  cylindrical  pins  may  be  assigned  to  the  conical  wheel  and  teeth  constructed 
for  the  other. 

And  finally,  the  same  principles  and  methods  may  be  applied  to  the  construction  of  what  may  be 
called  bevel-face  gearing,  as  shown  in  Fig.  2149.  In  this  case  the  action  is  exactly  the  same  as  that 
of  two  rolling  cones,  the  axes  of  the  teeth  in  one  wheel  being  rectilinear  elements  of  one,  while  the 
pins  in  the  other  project  normally  from  the  pitch-cone.  C.  W.  MacC. 

GEARING,  FRICTIONAL.  As  used  in  the  lumbering  regions  in  this  country  to  transmit  motion 
in  wood-working  machinery,  frictional  gearing  usually  consists  of  smooth-surfaced  wheels  in  contact, 
one  pulley  being  made  of  iron,  the  other  of  wood  or  iron  covered  with  wood.  Where  it  is  practica- 
ble, the  wooden  pulley  drives  the  iron,  wear  of  the  former  being  thus  saved.  For  driving  heavy  ma- 
chinery, the  wooden  drivers  arc  put  upon  the  engine-shaft,  and  each  machine  is  driven  by  a  separate 
countershaft.  Two  or  more  of  these  countershafts  are  usually  driven  by  contact  from  the  same 
wheel.  For  small  machinery  the  friction-drivers  are  put  upon  a  line-shaft  so  as  to  drive  a  small 
countershaft,  whence  power  is  taken  by  a  belt.  For  the  wooden  pulley,  basswood,  cottonwood,  and 
even  white  pine,  have  given  good  results  in  driving  light  machinery.  For  heavy  work,  where  from 
In  to  60  horse-power  is  transmitted  by  simple  contact,  soft  maple  is  preferable.  For  very  small  pul- 
leys leather  and  rubber  may  be  employed.     Paper  pulleys  have  yielded  excellent  results. 

All  large  drivers,  say  from  4  to  10  feet  in  diameter  and  from  12  to  30  inches  face,  should  have 
rims  of  soft  maple  6  or  7  inches  deep.  These  should  be  made  up  of  plank  H  to  2  inches  thick,  cut 
into  "  cants"  one-sixth,  one-eighth,  or  one-tenth  of  a  circle,  so  as  to  place  the  grain  of  the  wood  as 
nearly  as  practicable  in  the  direction  of  the  circumference.  The  cants  should  be  closely  fitted,  put 
together  with  white  lead  or  glue,  and  Btrongly  nailed  am!  bolted.  The  wooden  rim  should  be  made 
up^to  within  about  3  inches  of  the  width  of  the  finished  pulley,  and  be  mounted  on  one  or  two  heavy 
iron  "spiders"  with  6  or  8  radial  arms.  For  pulleys  above  6  feet  in  diameter,  there  should  be  8 
arms,  and  2  spiders  when  the  width  of  face  is  more  than  18  inches.  Upon  the  ends  of  the  arms 
are  Hat  "  pads,"  which  should  be  of  just  sufficient  width  to  extend  across  the  inner  face  of  the 
wooden  rim  as  described— that  is,  3  inches  less  than  the  width  of  the  finished  pulley.  These  pads 
are  gained  into  the  inner  side  of  the  rim,  the  gains  being  cut  large  enough  to  admit  keys  under  ami 
beside  the  pads.  When  the  keys  are  well  driven,  strong  lag-screws  are  put  through  the  arm  into 
the  rim.  This  done,  an  additional  round  is  put  on  each  side  of  the  rim  to  cover  the  holt-heads  and 
secure  the  keys  from  working  out.  The  pulley  is  now  put  in  its  place  on  the  shaft  and  keyed,  the 
(due-  trued  up,  and  the  face  turned  off  with  the  utmost  exactness.  For  small  drivers,  the  best 
construction  is  to  make  an  iron  pulley  of  about  8  inches  less  diameter  and  ?>  inches  less  face  than 
the  pulley  requited.  Have  I  lugs  about  an  inch  square  cast  across  the  face  of  this  pulley.  Make  a 
wooden  vim  1  inches  deep,  with  lace  equal  to  that  of  the  iron  pulley,  and  the  inside  diameter  equal 
to  the  outer  diameter  of  the  iron.  Drive  the  rim  snugly  on  over  the  rim  of  the  iron  pulley,  having 
cut  gains  to  receive  the  lugs,  together  with  a  hard-wood  key  beside  each.  Now  add  a  round  of  cants 
upon  each  side,  with  theirlnner  diameter  less  than  the  first,  so  as  to  cover  the  iron  rim.  The  wood 
should  be  thoroughly  seasoned,  and  the  fibre  should  be  in  a  line  with  the  work. 

As  to  the  width  of  face  required  in  friction-gearing :  When  the  drivers  are  of  maple,  a  width  of 
face  equal  to  that  required  for  a  good  leather  belt  (single)  to  do  the  same  work  is  sufficient.  (See 
Belting.)     The  driver-pulleys  are  similar  to  belt-pulleys,  but  much  heavier.     The  arm  should  be 

Btraight,  and  there  should  be  two  sets  of  arms  if 
the  pulley  is  above  It)  inches.  A  good  rule  is  to 
make  the  thickness  of  rim  2£  per  cent,  of  the  di- 
ameter. To  secure  accuracy,  they  should  be  fitted 
and  turned  upon  the  shaft  and  carefully  balanced. 
Limited  experiments  in  order  to  compare  fric- 
tional gearing  with  belted  pulleys  have  indicated 
that  the  traction  of  friction-wheels  is  greater  than 
that  of  belted  pulleys,  and  considerably  more  than 
is  usually  supposed   to  be  obtained   from  belts 


— ^X 

•^  v-  r~ 

upon  pulleys  of  either  wood  or  iron ;  and  that, 
while  there  is  a  marked  falling  off  in  the  adhesion 
of  the  belt  as  the  work  increases,  that  of  the  fric- 
tion augments  as  the  labor  becomes  greater.    Also, 
that  the  difference  in  the  pressure  required  just 
to  do  the  work,  and  that  necessary  to  do  it  with- 
out slip,  advances  in  an  increasing  ratio  with  the 
work  of  the  belt ;  but  in  the  friction-pulley  it  is 
almost  constant  throughout  the  whole  range  of 
experiments.     Details  of  these  tests  will  be  found 
in  the  papers  from  which  this  abridgment  is  made. 
Bevel  Frictional  Gearing. — In  building  this  gearing,  the  iron  cone  or  pulley  is  made  similar  to  a 
bevel-pinion,  except  as  to  the  teeth,  instead  of  which  there  is  a  smoothly-turned  face.     In  making 
the  wooden  driver,  place  a  square  across  the  smaller  end  of  the  finished  iron  pulley,  and  set  a  bevel 


to  it,  as  shown  at  (1)  in  Fig.  2150.  This  will  give  the  correct  bevel  for  the  face  of  the  driver. 
Next,  upon  any  plane  surface  draw  the  lines  A  B  and  A  C,  making  the  length  of  A  B  just  equal  to 
the  larger  diameter  of  the  iron  pulley,  and  the  angle  at  A  a  right  angle.  Then  with  the  square  and 
bevel  draw  the  lines  B  C  and  A  D.  The  distance  ^4  C  is  the  diameter  required  for  the  driver,  and 
the  other  dimensions  are  easily  obtained. 

To  obtain  the  bevels  for  pulleys  to  work  on  shafts  placed  at  acute  angles,  draw  the  lines  as  in  (2), 
Fig.  2150.  Let  A  B  represent  the  driving-shaft.  Make  A  C  equal  in  length  to  one-half  the  diame- 
ter of  the  driving-pulley.  Draw  the  line  G  I)  at  the  angle  to  which  the  shafts  are  to  be  set,  and 
at  a  right  angle  to  this  line  draw  C  E  in  length  equal  to  half  the  diameter  of  the  other  pulley. 
From  the  point  E,  parallel  to  CD,  draw  E E,  which  will  represent  the  other  shaft.  From  the  point 
of  intersection  of  this  and  the  line  A  B  draw  the  line  G  C,  which  will  give  the  bevels  for  both  pulleys. 

If  not  above  2A  feet  in  diameter,  the  driver  may  be  built  on  a  hub-flange,  a  disk  of  iron  of  about 
two-thirds  the  diameter  of  the  pulley  with  a  hub  projecting  on  one  side.  The  hub  should  extend 
half  an  inch  beyond  the  thickness  of  the  wood  to  receive  an  annular  disk  of  smaller  diameter, 
through  which  the  whole  may  be  securely  bolted  together.  Upon  the  flange  around  the  hub  the  pul- 
ley should  be  built.  The  first  2  or  3  inches  to  form  the  back  should  be  of  hard  wood  put  on  radially. 
For  the  remainder,  use  soft  maple.  When  the  wood  is  built  up  to  sufficient  thickness,  the  other 
flange  should  be  put  on,  and  the  whole  bolted  together  and  turned  to  the  exact  diameter  and  bevel 
required.  For  a  large  bevel-driver  it  is  best  to  use  an  iron  centre  with  arms,  and  a  flanged  rim  some- 
thins;  like  that  of  a  car-wheel.  The  diameter  of  the  rim  or  cylinder  should  be  a  few  inches  less  than 
the  smaller  diameter  of  the  pulley,  and  that  of  the  flange  something  less  than  the  larger  diameter. 
Upon  this  wheel  the  wooden  rim  is  built,  as  directed,  upon  the  hub-flange,  except  that  the  bolts  must 
be  put  in  as  the  work  progresses,  so  that  subsequent  layers  will  cover  the  heads ;  and  the  pulley  is 
finished  without  the  smaller  flange.     Fig.  2151  shows  a  cross-section  of  this  pulley. 

The  foregoing  is  abridged  from  papers  on  "  Frietional  Gearing,"  by  E.  S.  Wicklin,  in  the  Scientific 
American,  vol.  xxvi.,  227,  et  seq. 

Grooved  Frietional  Gearing. — Robertson's  grooved-surface  fractional  gearing  consists  of  wheels  or 
pulleys  geared  together  by  frietional  contact,  in  which  the  driving  surfaces  are  grooved  or  serrated 
annularly,  the  ridges  of  one  surface  entering  the  grooves  of  the  other.  A  lateral  wedging  action  is 
obtained,  which  augments  the  adhesion  of  the  surfaces,  as  compared  with  flat  friction  surfaces,  in 
the  ratio  of  9  to  1.  That  is,  the  grooved  wheels  require  a  force  of  3  lbs.  acting  at  their  circumfer- 
ence to  make  them  slip,  for  every  2  lbs.  applied  on  the  axis  ;  whereas  two  flat  surface-wheels  would 
require  (2  x  9  =  )  18  lbs.  of  pressure  on  the  axis  to  enable  them  to  resist  a  force  of  3  lbs.  acting  on 
the  circumference.  The  grooves  are  made  of  V  shape,  for  which  50°  is  the  most  suitable  angle. 
The  pitch  of  the  grooves  is  varied  according  to  the  velocity  and  the  power  to  be  transmitted — from 
one-eighth  to  three-quarters  of  an  inch  ;  the  ordinary  pitch  is  three-eighths  of  an  inch.  See  a  paper 
by  Mr.  James  Robertson  on  "  Grooved-Surface  Frietional  Gearing,"  in  "  Proceedings  of  Institution  of 
Mechanical  Engineers,"  1856. 

GENEVA  STOP.  Where  a  train  of  wheels  is  set  in  motion  by  a  spring  inclosed  in  a  barrel,  it 
becomes  of  consequence  not  to  over-wind  the  spring.  The  Geneva  stop,  Fig. 
2152,  has  been  contrived  with  the  view  of  preventing  such  an  occurrence,  and 
will  be  found  in  all  watches  which  have  not  a  fusee.  A  disk  A,  furnished  with 
one  projecting  tooth  P,  is  fixed  upon  the  axis  of  the  barrel  containing  the  main- 
spring, and  is  turned  by  the  key  of  the  watch.  Another  disk,  B,  shaped  as  in 
the  drawing,  is  also  fitted  to  the  cover  of  the  barrel,  and  is  turned  onward  in 
one  direction  through  a  definite  angle  every  time  that  the  tooth  P  passes  through 
one  of  its  openings,  being  locked  or  prevented  from  moving  at  other  times  by 
the  action  of  the  convex  surface  of  the  disk  A.  In  this  manner  each  rotation 
of  A  will  advance  B  through  a  certain  space,  and  the  motion  will  continue  until 
the  convex  surface  of  A  meets  the  convex  portion  E,  which  is  allowed  to  re- 
main upon  the  disk  B  in  order  to  stop  the  winding  up.  The  winding  action 
having  ceased,  the  disks  will  return  to  their  normal  positions  as  the  mechanism 
runs  down.  Instead  of  supposing  A  to  make  complete  revolutions,  let  it  oscil- 
late to  and  fro  through  somewhat  more  than  a  right  angle ;  then  B  will  oscillate 
in  like  manner,  and  will  be  held  firmly  by  the  opposition  of  the  convex  to  the 
concave  surface,  except  during  the  time  that  P  is  moving  in  the  notch. 

GIB  AND  COTTER.  A  method  of  connecting  separate  parts  of  a  machine.  Sometimes  one  of 
the  connected  pieces  is  required  to  move  while  the  other  remains  stationary ;  frequently  both  pieces 
have  motion  imparted  to  them,  as  in  the  case  of  the  connecting-rod  of  a  steam-engine,  when  the 
connection  at  the  end  is  often  made  by  means  of  gibs,  a  cotter,  and  a  strap.  Again,  both  connected 
pieces  may  be  stationary,  in  which  case  the  principle  of  the  connection  is  the  same. 

There  are  three  forms  of  this  device  :  1.  The  simple  cotter  without  gibs ;  2.  A  cotter  and  one  gib ; 
3.  A  cotter  and  two  gibs.  Of  the  second  and  third  forms  there  are  a  variety  of  designs,  and  various 
means  are  employed  to  force  home  the  cotter  and  to  keep  it  there. 

The  cotter  itself  is  a  tapered  piece  of  metal,  generally  resembling  in  form  and  action  a  wedge, 
but  with  this  difference,  that  the  wedge  is  used  to  force  asunder  parts  of  the  same  piece  or  differ- 
ent pieces,  while  the  cotter  is  employed  to  draw  together  by  means  of  available  parts  two  or  more 
pieces  of  metal.  The  amount  of  taper  givcu  to  the  cotter  must  not  exceed  the  angle  of  repose  of 
metal  upon  metal,  which  for  greased  surfaces  may  be  taken  at  about  4°.  Some  authorities  recom- 
mend a  taper  of  1  in  24  to  1  in  48  for  simple  cotters,  and  1  in  8  to  1  in  16  when  the  slacking  of  the 
cotter  is  prevented  by  a  screwed  prolongation  of  the  gib ;  a  common  rule  is  to  make  the  taper  one- 
half  to  three-fourths  of  an  inch  to  each  foot  of  length. 

Colter  connecting  two  Pieces  wit/tout  a  Gib. — In  Fig.  2153  is  shown  an  example  of  the  use  of  a 



cotter  without  a  gib  being  employed  in  conjunction  with  it ;  it  here  maintains  the  bolt  c  in  the  hole 
made  in  the  piece  b  to  receive  it.     The  action  of  the  cotter  is  simply  to  wedge  itself  tightly  into 



the  pieces,  and  maintain  its  hold  by  the  grip  thus  induced 
keeps  its  place  the  bolt  c  cannot  be  removed  from  b. 

Colter  connecting  two  Pieces  when  <>nr  (lil>  ia  used. — Fi 
A  is  the  cotter,  li  the  gib,  and  C  the  strap.  The  shape 
of  the  strap  is  shown  more  clearly  in  Tig.  2156,  ",  6, 
and  c  being  the  openings  in  it. 

(Jotter  and  lino  Gils. — Fig.  2156  shows  a  connectm"- 

It  is  quite  evident  that  so  long  as  d 
2154  gives  two  views  of  a  connectinpr-rod. 

rod  head,  held  together  by  a  strap,  cotter,  and  two 
gibs;  the  strap  is  marked  ss,  the  cotter  «,  and  the  two 
gibs  b  respectively.  They  firmly  hold  the  brasses  at 
the  end  of  the  rod  in  their  places.  The  advantage  of 
two  gibs  is,  that  they  keep  the  strap  firmer  against  the  brasses.  The  screw  which  forms  the  lower 
part  of  the  gib  serves  to  prevent  the  cotter  from  falling  or  being  jerked  out  when  the  engine  is  in 
motion.  After  the  strap  .vis  put  on  the  connecting-rod,  the  gib  b  is  inserted,  and  then  the  nut  c  is 
placed  so  that  when  the  key  a  is  put  in  the  nut  can  be  screwed  up.  The  key  is  driven  home  with 
the  hammer,  the  nut  c  being  slackened  to  allow  it  to  come  down.  When  it  is  made  as  tight  as  is 
required,  the  nut  <1  is  put  on  and  screwed  up  tightly.  Then  c  is  screwed  down,  and  thus  the  two  pre- 
vent the  key  from  becoming  slack.  The  hole  for  the  bolt  at  c  must  be  made  elliptical,  so  as  to  allow 
the  key  to  come  down  without  bending  the  bolt. 

The  foregoing  is  abridged  from  "Principles  of  Machine  Construction,"  Tomkins,  London  and 
Glasgow,  1878. 

GIG.     See  Cloth-finishing  Machinery. 

GIX,  COTTON.     See  Coxton-Gi». 

GIN,  HOISTING.     See  Cranes  and  Derricks. 

GIRDERS.     See  Carpentry. 

GLASS,  MANUFACTURE  OF.  Gla-s  is  an  amorphous  substance,  hard  and  brittle  at  ordinary 
temperatures,  liquid  or  soft  at  a  high  heat,  transparent  or  translucent,  colored  or  colorless,  and  pre- 
senting a  special  fracture.  It  is  the  result  of  the  combination  of  silicic  acid  (silex)  with  several  of 
the  following  bases  :  potash,  soda,  lime,  magnesia,  oxide  of  lead,  oxide  of  iron,  and  aluminum.  The 
various  sorts  of  glass  are  distinguished  with  regard  to  their  composition,  their  mode  of  fabrication, 
and  their  uses. 

Window-pane  glass,  mirrors,  and  glass  for  fable  rise  are  formed  of  the  same  elements  associated  in 
different  proportions.     These  elements  are  silex,  lime,  and  soda. 

Bohemian  glass,  which  is  used  in  Germany  for  the  production  of  drinking-vessels,  is  a  silicate  with 
a  potash  and  lime  base.  It  contains  besides,  as  do  all  other  kinds  of  glass,  a  small  quantity  of  alu- 
minum and  of  oxide  of  iron,  obtained  either  from  the  crucible  in  which  it  is  melted,  or  from  the 
more  or  less  purified  materials  employed  for  its  production. 

Boltle-glass  contains,  together  with  the  silex,  soda,  or  potash,  lime,  magnesia,  aluminum,  and  iron 

Crystal  is  a  glass  having  a  base  of  lead  oxide  and  potash.  Flint-glass,  a  dense  substance  used  for 
optical  purposes,  and  strass,  employed  in  imitating  precious  stones,  are  of  similar  elementary  consti- 
tution, though  the  ingredients  are  in  different  proportions. 



The  enamels  contain,  in  addition  to  the  normal  glass  ingredients,  oxide  of  tin  or  arsenious  acid, 
which  gives  them  the  opacity  that  distinguishes  them  from  all  other  classes  of  glass. 

Colored  glass  obtains  its  tints,  which  may  be  infinitely  varied,  from  various  metallic  oxides,  from 
some  metals,  carbon,  and  sulphur.  Many  kinds  of  colorless  glass  contain  a  small  quantity  of  oxide 
of  manganese,  this  substance  being  introduced  in  order  to  obtain  a  whiter  glass. 

To  these  may  be  added  the  soluble  glass,  which  is  a  simple  silicate  of  soda  or  of  potash,  or  a  mix- 
ture of  the  two  silicates. 

The  specific  gravity  of  glass  varies  with  its  composition,  from  2.4  to  about  3.6,  although  optical 
glass  of  greater  specific  gravity  is  sometimes  made,  amounting  in  some  instances  to  5.  Its  density 
and  also  its  refractive  property  are  increased  with  the  proportion  of  oxide  of  lead  it  contains.  Brit- 
tleness  is  a  quality  that  limits  the  alteration  of  the  shape  of  glass  within  narrow  bounds,  after  it  has 
cooled  ;  but  when  softened  by  heat  while  it  is  highly  tenacious,  no  substance  is  more  easily  moulded 
into  any  form,  and  it  can  be  blown  by  the  breath  into  hollow  vessels  of  which  the  substance  is  so 
thin  that  they  may  almost  float  in  the  air.  It  may  also  be  rapidly  drawn  out  into  threads  of  several 
hundred  feet  in  length ;  and  these  have  been  interwoven  in  fabrics  of  silk,  producing  a  beautiful 
effect.  In  the  soft  plastic  state  it  may  be  cut  with  knives  and  scissors  like  sheets  of  caoutchouc. 
It  is  then  inelastic  like  wax ;  but  when  cooled  its  fibres  on  being  beaten  fly  back  with  a  spring,  and 
hollow  balls  of  the  material  have,  when  dropped  on  the  smooth  face  of  an  anvil  from  the  height  of 
10  or  12  feet,  been  found  to  rebound  without  fracture  to  one-third  or  one-half  the  same  height.  It 
has  the  valuable  property  of  welding  perfectly  when  red-hot,  and  portions  brought  together  are  in- 
stantly united.  When  moderately  heated  it  is  readily  broken  in  any  direction  by  the  sudden  contrac- 
tion caused  by  the  application  of  a  cold  body  to  its  surface.  It  is  also  divided  when  cold  by  break- 
ing it  along  lines  cut  to  a  slight  depth  by  a  diamond,  or  some  other  extremely  hard-pointed  body  of 
the  exact  form  suited  for  this  purpose ;  and  it  may  be  bored  with  steel  drills,  provided  these  are  kept 
slightly  moistened  with  water,  which  forms  a  paste  with  the  powder  produced.  Oil  of  turpentine, 
either  alone  or  holding  some  camphor  in  solution,  is  also  used  for  the  same  purpose.  Copper  tubes 
fed  with  emery  also  serve  to  bore  holes  in  glass.  Acids  and  alkalies  act  upon  glass  differently  accord- 
ing to  its  composition,  and  reference  should  be  made  to  this  in  storing  different  liquids  in  bottles. 
Silicate  of  alumina  is  readily  attacked  by  acids,  and  bottles  in  which  this  is  in  excess  are  soon  cor- 
roded even  by  the  bitartrate  of  potash  in  wine,  and  by  the  reaction  the  liquor  itself  is  contaminated. 
A  glass  that  loses  its  polish  by  heat  is  sure  to  be  attacked  by  acids.  Oxide  of  lead  when  used  in 
large  proportion  is  liable  to  be  in  part  reduced  to  a  metallic  state  by  different  chemical  reagents,  and 
give  a  black  color  to  the  glass.     All  glasses  are  attacked  by  hydrofluoric  acid. 

Melting. — The  various  materials  entering  into  glass  manufacture  will  be  noted  as  each  class  of 
glass  is  described.  For  melting,  these  are  thoroughly  ground,  mixed  together,  and  sifted,  and  are 
incorporated  with  from  one-quarter  to  one-third  their  weight  of  broken  glass  before  being  introduced 
into  the  melting-pots.  The  latter  are  previously  heated  to  a  white  heat  in  the  furnace,  and  receive 
only  two-thirds  of  a  charge  at  a  time,  more  being  added  as  the  first  portion  melts  down.  The  pot 
being  at  last  filled  with  the  melted  "  metal,"  the  heat  is  raised  as  rapidly  as  possible,  and  the  prog- 
ress of  the  operation  is  judged  of  by  the  workman  dipping  iron  rods  from  time  to  time  into  the 
mixture  and  examining  the  appearance  of  the  drops  withdrawn.  A  nearly  homogeneous  product, 
which  becomes  transparent  on  cooling,  indicates  that  the  most  refractory  ingredients  have  been  all 
dissolved.  Their  mixture  is  facilitated  by  the  continual  disengagement  of  carbonic  acid  gas,  which 
in  its  escape  causes  the  whole  to  be  thrown  into  ebullition.  Some  of  the  gas  remains  in  the  mass, 
rendering  it  spongy  and  full  of  vesicles.  Unless  in  the  manufacture  of  the  finer  qualities  of  glass, 
for  which  the  purest  materials  are  employed,  there  is  also  a  scum  called  "  glass  gall  "  or  "  sandiver  " 
floating  on  the  surface,  consisting  of  the  insoluble  matters,  and  the  sulphates  of  soda  and  lime  not 
taken  up  by  the  mixture.  This  is  removed  by  ladling,  and  the  metal  is  next  "  fined,"  which  is  done 
by  increasing  the  heat  to  the  highest  degree,  and  keeping  the  contents  of  the  pots  in  a  state  of  per- 
fect fluidity  for  from  10  to  30  hours  ;  in  this  time  the  bubbles  disappear,  and  the  insoluble  matters 
settle  to  the  bottom.  The  furnace  is  then  allowed  to  cool  until  the  metal  has  become  viscid,  so  that 
it  mav  be  taken  out  and  worked  ;  and  it  is  afterward  kept  at  a  sufficiently  high  temperature  to  main- 
tain the  glass  in  this  condition,  that  it  may  be  used  as  required.  For  construction  of  glass  furnaces 
and  pots,  see  Furnaces,  Glass. 

Window-Glass. — The  glass  commonly  used  for  window-panes  is  one  of  the  hardest  varieties,  and  is 
of  unsuitable  quality  for  shaping  into  vessels  or  manufacturing  by  cutting  or  grinding.  The  follow- 
ing table  shows  the  composition  of  several  varieties : 

French  glass 

Belgian  glass 

English  glass 

Very  white  potash  glass 

Glass  easily  tarnished,  bad  quality 




























Oxides  of  Iron 
and  Manganese. 





The  ingredients  used  are  sand,  sulphate  of  soda,  and  lime  in  the  form  of  carbonate  or  slacked  lime. 
In  the  north  of  France  and  in  Belgium  these  are  employed  in  the  following  proportions:  whitesand, 
100  parts;  sulphate  of  soda,  35  to  40 ;  limestone,  25  to  35  ;  coke  powdered,  1.5  to  2  ;  binoxide  of 
manganese,  0.5 ;  and  glass  scrap  in  variable  quantity,  usually  in  the  same  proportion  as  sand.  Ar- 
senious acid  is  sometimes  added  to  act  as  a  decolorizing  agent  and  to  facilitate  the  fining.  English 
makers  produce  a  very  fine  white  glass  for  photography,  and  for  covering  pictures  in  frames,  in 



closed  pots,  with  the  following  ingredients:  Fontainebleau  or  American  sand,  100  parts;  carbonate 
of  soda  at  90°,  36  ;  nitrate  of  soda,  5;  powdered  slacked  lime,  12  ;  and  arsenious  add,  0.5. 

There  are  three  kinds  of  glass  which  come  under  the  general  heading  of  window-glass,  namely, 
sheet,  crown,  and  plate.  All  of  these  differ  in  their  manufacture.  Crown-glass  is  first  blown  into 
a  globe  or  sphere  and  flattened  out  into  a  circular  disk  ;  sheet-glass  is  formed  into  a  cylinder,  which 
is  opened  out  into  a  sheet ;  and  plate-glass  is  east  on  huge  tables. 

Sheet-Glaaa. — In  the  manufacture  of  sheet-glass  two  furnaces  are  generally  used,  one  for  melting 
or  making  the  glass,  and  the  other  for  reheating  it  during  the  process  of  blowing.  The  latter  is 
usually  of  oblong  form,  with  4,  5,  or  6  holes  on  each  side  for  as  many  workmen.  On  each  side  of 
this  furnace  is  a  pit  about  7  feet  deep,  16  feet  wide,  and  as  long  as  the  furnace;  over  this  at  inter- 
vals of  about  2  feet  are  erected,  in  front  of  each  hole  of  the  furnace,  wooden  stagings  or  platforms, 

upon  which  the  workman  stands  when  swinging 
2157.  the  cylinder  to  and  fro  and  over  his  head.     The 

manufacture  may  be  divided  into  three  process- 
es :  1,  blowing  the  cylinder ;  2,  flattening  it  out 
into  a  sheet ;  3,  polishing  the  sheet.  The  oper- 
ation of  blowing  is  represented  in  Fig.  2157,  and 

2158.  2159. 

begins  with  the  collection  of  a  sufficient  quantity 
ol  metal  from  the  pot  at  the  end  of  the  pipe.  A 
massive  glass  ball  is  thus  attached  round  the 
knot)  of  the  pipe,  which  must  lie  pushed  for- 
ward with  a  flatting-iron  until  an  annular  groove 
is  produced.  When  this  operation  is  completed,  the  blower  rounds  the  bull  by  rolling  it  on  the 
marver,  and  distends  it  slightly  by  bloving.  It  then  assumes  the  form  represented  in  Fig.  2158,  from 
which  it  will  be  seen  that  the  mass  of  glass  is  thickest  in  front,  as  from  that  part  it  has  to  be  dis- 
tended and  lengthened  into  a  cylinder.  In  the  subsequent  operations,  it  first  assumes  the  width  of 
the  future  cylinder  and  then  the  length.  With  this  object  in  view,  the  workman,  after  having  re- 
warmed  the  ball  of  glass,  holds  it  perpendicularly  above  his  head,  and  blows  into  it.  The  heavy  bot- 
tom, yielding  with  less  ease  to  the  blast,  admits  of  the  distention  of  the  width,  and  a  flattened  bottle 
is  formed,  Fig.  2169.  As  soon  as  the  proper  width  is  attained,  the  pipe  is  quickly  inverted,  so  that 
the  ball  is  undermost,  and  an  incessant  swinging  motion  is  then  kept  up  with  a  constant  blast.  Fur- 
ther distention  is  thus  effected,  but  from  the  bottom  only,  as  the  thinner  sides  have  by  this  time  cooled, 
and  in  consequence  of  the  swinging  motion  in  the  direction  of  the  length,  so  that  the  bottle  acquires 



the  form  represented  in  Fig.  2160  by  the  time  that  the  glass  has  so  far  cooled  as  to  be  no  longer 
expansible.  If  the  swinging  were  intermitted,  the  bottle  would  be  distended  in  all  directions,  and 
present  the  form  indicated  by  the  circular  line.  By  repeated  warming,  swinging,  and  blowing,  the 
form  Fig.  2161  is  gradually  produced,  which  is  of  the  proper  length  of  the  cylinder.  It  is  then  coni- 
cal, and  terminated  by  a  semicircle,  in  the  middle  of  which,  at  c,  is  the  thinnest  part  of  the  vessel. 



When  the  workman  blows  air  into  the  pipe,  and  closes  the  aperture  with  his  thumb  before  withdraw- 
ing the  pipe  from  his  mouth,  the  air  expands  and  exerts  great  tension  upon  the  sides  of  the  cylinder ; 
if  the  weakest  part,  at  c,  is  now  held  in  the  flame,  it  will  be  blown  out  and  burst.  The  cylinder  hav- 
ing thus  been  opened  as  represented  in  Fig.  2162,  the  next  object  is  to  extend  the  somewhat  uneven 
and  thick  margin  of  the  aperture,  and  reduce  it  to  the  proper  dimensions,  while  at  the  same  time  the 
other  parts  are  straightened  and  acquire  a  uniform  diameter,  as  is  shown  in  Fig.  2163.  Prominent 
portions,  which  may  sometimes  project,  are  cut  away  with  the  scissors. 

According  to  the  size  of  the  cylinder,  it  may  be  either  blown  at  once,  or  it  will  require  to  be  re- 
heated several  times.  When  very  long  and  wide  cylinders  are  blown,  the  lower  portion  is  liable  to 
become  too  thin ;  an  extra  portion  of  glass  must  then  be  incorporated  with  it  before  the  opening 

The  neck  and  curvature  where  the  pipe  was  attached  to  the  cylinder  have  now  to  be  removed,  in 
order  to  spread  the  whole  out  in  the  form  of  a  plate,  and  the  cylinder  must  be  cut  open  lengthwise. 


The  cylinder,  supported  by  an  assistant  upon  a  wooden  rod,  is  therefore  turned  round  two  or  three 
times  in  the  curve  of  a  bent  iron,  heated  to  redness,  as  shown  in  Fig.  2164,  and  a  drop  of  water  is 
allowed  to  fall  upon  the  heated  line,  which  fractures  the  glass  and  detaches  the  cap.  In  a  similar 
manner,  but  in  a  straight  direction,  a  crack  is  made  longitudinally,  and  the  cylinder  is  then  prepared 
for  spreading  or  flatting,  Fig.  2165.  Instead  of  cracking  the  cylinder  by  this  means,  the  cap  of  the 
cylinder  is  sometimes  taken  off  by  winding  around  it  a  thread  of  hot  glass,  and  after  removing  the 
latter  applying  a  piece  of  cold  iron  to  any  point  which  the  thread  covered.  After  trimming  the  other 
end  by  cutting  off  about  2  inches  in  length  with  a  diamond,  the  cylinder  is  split  open  longitudinally  by 
drawing  along  its  inside  surface  a  diamond  attached  to  a  long  handle  and  guided  by  a  wooden  rule. 

Flatting  is  conducted  in  furnaces  purposely  constructed,  the  principal  parts  of  one  of  which 
are  shown  in  Fig.  2166.  The  flame  first  plays  upon  the  flatting-hearth  C  before  entering  the  anneal- 
ing or  cooling  furnace  B,  which  is  also  heated  directly  by  the  fire,  when  it  escapes  through  the  flue 
or  channel  D,  by  which  the  cylinders  are  introduced  to  be  subsequently  removed.  The  flattener 
stands  in  front  of  the  aperture  I,  the  workman  engaged  at  the  cooling-furnace  before  m  ;  and  an 
assistant  pushes  the  cylinder  oooo  along  the  railway  p.  The  most  essential  part  of  the  furnace, 
however,  is  the  spreading-plate  or  fatting -atone  q  and  q .  This  must  be  perfectly  even,  without  any 
roughness  or  inequalities  which  would  scratch  the  glass  or  make  it  lumpy ;  it  must  be  unalterable  in 
the  fire,  and  of  a  size  somewhat  larger  than  the  flattened  cylinders.  A  plate  of  this  description  is 
usually  manufactured  from  fire-proof  clay  mixed  with  cement  (either  ground  fragments  of  burnt  clay 
of  the  same  kind,  or  fine  sand,  or  ground  quartz),  strongly  beaten  during  drying,  then  burnt,  and 
lastly  ground  smooth  ;  it  is  laid  upon 

a  bed  of  sand  and  in  contact  with  a  ai°°' 

second  table  of  the  same  sort  in  the 
cooling-oven.  To  make  quite  sure 
that  no  injury  shall  be  sustained  by 
the  plates  upon  the  flatting-stone,  it 
is  customary  to  cover  this  previously 
with  a  lager,  which  is  a  thick  plate  of 
glass  expressly  blown  for  this  pur- 
pose. These  lagers  are  soon  devitri- 
fied,  which  is  of  no  moment  so  long 
as  the  surface  remains  smooth ;  this, 
however,  does  not  last  long,  and  fre- 
quent renewal  of  the  lager  becomes 
necessary.  Lastly,  to  prevent  the  cyl- 
inders from  attaching  themselves  to 
the  lager,  the  flattener,  in  some  manu- 
factories, throws  a  handful  of  lime 
into  the  furnace,  which  is  carried  as 
fine  dust  by  the  flame  and  spread  over 
the  lager.  The  temperature  in  the 
flatting-furnace  must  only  be  just  suf 
ficient  to  soften  the  cylinders,  while 
in  the  cooling-furnace  it  must  not  at- 
tain that  point.  _ 

The  spreading  operation  is  commenced  by  introducing  the  cylinders  into  the  warming-tube  D.  The 
further  the  cvlinders  are  pushed  forward  by  those  succeeding  them,  the  more  they  become  heated, 
until  they  begin  to  soften  on  reaching  the  flatting-stone.     They  are  then  taken  by  the  workman  with 



a  rectangular  bent  iron,  and  placed  upon  the  lager  with  the  cut  side  uppermost,  where  they  open  of 

themselves,  and  are  easily  straightened  and  made  even. 

For  this  latter  purpose,  a  rod  of  iron,  fur- 
nished at  the  end  with  a  wooden  polisher, 
Fig.  2167,  is  employed,  and  this  is  dipped 
into  water  each  time  it  is  used.  When  all 
the  curvatures  and  lumps  have  been  reduced, 
the  sheet  is  pushed  backward  into  the  an- 
nealing-oven, where  it  cools  down  and  is 
placed  in  an  upright  leaning  position.  Be- 
tween every  80  or  40  sheets  an  iron  rod  s  s 
is  inserted,  and  the  operation  is  continued 
until  the  whole  furnace  is  filled. 
Fig.  2168  is  an  elevation  of  a  flatting-furnace  in  section,  with  three  annealing-arches  of  the  ordi- 
nary description.  Fig.  2169  is  a  ground  plan  of  the  same.  In  Fig.  2170  are  elevations  of  two  end 
views  of  the  flatting-furnace,  a  b  is  the  spreading-furnace,  divided  into  two  compartments  by  the 
partition  c  ;  dd  are  two  sets  of  fire-bars,  on  which  wood  must  be  burnt ;  e  is  the  spreading  or  flat- 
ting stone  oi  the  furnace,  which  must  be  perfectly  smooth  and  even ;  i  is  an  opening  through  which 

21 6S. 

the  cylinder  is  placed  in  the  furnace  previous  to  being  laid  on  the  flatting-stone  e  ;  h  is  the  opening 
through  which  the  workman  spreads  the  cylinder  into  a  flat  sheet  of  glass  ;  /  is  the  opening  through 
which  the  sheet  of  glass  is  removed  to  the  table  or  bed  //,  in  the  compartment  b.  The  upper  side  of 
the  table  ,7  is  made  of  stone,  similar  to  that  employed  as  the  flattening  surface.  It  is  fixed  to  an 
iron  framework  on  wheels,  and  is  kept  at  a  proper  degree  of  heat  by  remaining  in  the  furnace,  as 
shown  in  the  drawing.  The  carriage  runs  on  a  railway  in  front  of  the  annealing-arches,  where  the 
sheet  is  transferred  in  the  usual  way. 

The  cylinder  is  placed  on  the  flatting-Stone,  and  is  split  lengthwise  by  passing  a  red-hot  iron  bar  k 
from  end  to  end,  a  little  charcoal  powder  being  previously  sprinkled  on  the  inner  surface  of  the 


cylinder.  It  is  now  spread  out  into  a  sheet  by  pressing  the  same  on  the  flatting-stone,  by  means  of 
a  small  block  of  elder-wood,  fixed  on  an  iron  bar  m.  The  temperature  at  which  the  flatting  is  per- 
formed is  such  that  the  operation  does  not  occupy  more  than  a  minute. 

Two  improvements  have  been  introduced  in  this  operation.     One  consists  in  making  part  of  the 
floor  of  the  compartment  a  to  consist  of  a  movable  stone  about  10  inches  in  diameter,  on  which  the 




cylinder  is  placed.  It  is  gradually  exposed  on  all  sides  to  the  action  of  the  fire  by  causing  the  stone 
to  revolve  on  its  axis,  and  thus  the  objection  to  the  previous  plan  is  avoided,  where  one  side  of  each 
cylinder  became  so  much  hotter  than  the  other. 

Annealing  usually  requires  from  24  to  36  hours.     From  the  annealing-oven  the  sheets  are  taken  to 
the  warehouse,  where  they  are  smoothed,  polished,  assorted,  and  cut  into  panes  of  the  required 


dimensions.  The  former  method  of  grinding  and  polishing  sheet-glass  by  imbedding  the  sheets  in 
plaster  of  Paris  proved  inadequate  to  remove  the  defects  in  the  glass  consequent  upon  the  mode  of 
manufacture.  The  chief  of  these  was  the  undulating  or  wavy  appearance  of  the  surface,  called 
cockles,  which  was  attributed  to  the  difference  of  diameter  between  the  inner  and  outer  surfaces  of 
the  cylinder,  and  which  caused  objects  seen  through  the  glass  to  be  distorted.  Notwithstanding  the 
glass  was  made  very  thick,  after  the  superficial  roughness  was  removed  the  result  was  a  thin  sheet 
much  inferior  to  plate-glass.  The  ingenious  process  devised  by  Mr.  James  Chance  for  producing 
patent  plate-glass,  which  is  now  used  in  England  and  most  factories  on  the  continent,  is  one  of  the 
most  important  improvements  in  the  manufacture.  By  removing  the  thin  outer  surface  of  the  glass 
by  this  method,  an  evenness  and  a  polish  are  secured,  even  on  the  thinnest  sheet,  which  make  it  in 
many  respects  equal  to  plate-glass,  and  far  superior  to  the  sheet-glass  produced  by  the  old  process. 
The  improved  method  consists  in  placing  the  sheet  to  be  ground  and  polished  upon  a  flat  surface 
covered  with  a  piece  of  damp  soft  leather  or  cotton  cloth.  A  slight  pressure  applied  to  the  glass 
causes  it  to  adhere  to  the  surface  of  cotton  or  leather,  and  by  thus  producing  a  vacuum  the  entire 
sheet  is  firmly  maintained  in  a  flat  position  by  atmospheric  pressure.  The  exposed  surfaces  of  two 
sheets  fixed  in  this  manner  are  rubbed  against  each  other  in  a  horizontal  position  by  machinery, 
emery  and  water  being  constantly  supplied  to  keep  up  the  friction.  Both  sides  of  the  sheet  are 
polished  in  this  manner,  with  only  a  slight  diminution  of  the  thickness  of  the  glass.  After  the 
removal  of  the  sheets  from  these  surfaces,  they  resume  by  their  own  elasticity  their  original  shape, 
which  is  often  more  or  less  curved.  The  final  polish  is  given  to  the  sheets  by  a  process  similar  to 
that  used  in  polishing  plate-glass.  In  each  process  through  which  the  glass  has  passed  it  was  ex- 
posed to  some  imperfection,  and  some  of  the  sheets  bear  the  peculiar  defects  of  them  all  and  are  of 
little  value  ;  others  are  suitable  for  inferior  uses,  and  but  few  are  perfect.  The  wide  difference  be- 
tween the  quality  of  the  best  and  the  worst  sheets  is  indicated  by  the  fact  that  the  former  are  valued 
at  three  times  more  than  the  latter.  The  same  kind  of  material  is  used  in  the  production  of  both 
crown-  and  sheet-glass.  The  remarkable  brilliancy  of  surface  of  the  former  gives  to  it  a  certain 
advantage  over  sheet-glass  ;  but  the  larger  size  easily  attained  in  making  the  latter  gives  it  the  su- 
premacy in  commerce.  Of  crown-glass  it  is  difficult  to  obtain  panes  of  34  x  22  inches,  while  the 
usual  size  of  the  sheets  of  cylinder-glass  is  47  x  32  inches,  and  cylinders  are  occasionally  blown  77 
inches  in  length,  requiring  about  38  lbs.  of  glass. 

Crown- GVass.— Illustrations  of  the  furnace  used  for  melting  crown-glass  will  be  found  under  Fur- 
naces, Glass. 

When  a  certain  weight  of  glass,  a,  Fig.  2171,  has  been  collected  or  gathered  from  the  pots  on  the  «id 
of  the  tube  b,  it  is  fashioned  into  a  peculiar  form,  as  shown  in  the  figure,  on  a  solid  plate  of  cast-iron 
c,  called  a  marver.  Previous  to  the  operation  of  "  marvering,"  the  workman  cools  the  iron  pipe, 
which  has  become  heated  by  being  exposed  in  the  melting-furnace.  The  marver  c  is  placed  on  rollers 
for  the  convenience  of  moving  it  from  place  to  place  as  required.  When  the  mass  of  glass  has  as- 
sumed the  proper  form,  a  boy  blows  through  the  iron  tube,  while  the  workman  continues  to  roll  the 
ball  upon  the  marver.  During  the  previous  operation  of  "marvering,"  the  mass  of  glass  is  fashioned 
so  as  to  give  the  outer  extremity  a  conical  form,  the  extreme  end  of  which  becomes  the  outer  axis  of 
the  globe  during  the  operation  of  blowing.  This  outer  axis  is  called  the  "  bullion,"  and  during  the  ex- 
panding of  the  globe  the  workman  rollslhis  bullion  along  a  straight-edge.     The  piece  of  glass,  after 


— <o   

the  above  operation,  is  reheated  in  the  blowing-furnace,  and  expanded  by  the  workman  blowing 
through  the  iron  pipe,  until  it  is  so  far  cooled  as  to  require  another  "  heat."  When  it  has  been  blown 
to  the  proper  size,  Fig.  2172,  2,  it  is  again  exposed  to  the  heat  of  the  furnace,  when  the  workman, 
resting  the  pipe  on  an  iron  support,  during  which  time  the  neck  remains  cool,  causes  the  glass  globe, 
by  a  peculiar  motion  of  the  pipe,  to  assume  the  shape  shown  at  3.  This  last  operation  is  technically 
termed  "bottoming  the  piece."  It  is  then  removed  to  a  framing,  Fig.  2173,  where  it  rests  on  its 
edge  on  some  ground  charcoal  and  cinders  a.  Another  workman  then  attaches  a  strong  iron  rod, 
with  a  quantity  of  melted  glass  at  its  end,  to  the  centre  of  the  piece,  as  at  b.  The  "  blower  "now 
touches  the  neck  of  the  piece  at  c  with  an  iron  rod  previously  dipped  in  water,  and,  by  a  smart  blow 
on  the  iron  tube  d,  detaches  the  piece,  leaving  the  neck  open,  as  shown  at  4,  Fig.  2172. 

The  "  piece "  is  now  removed  to  the  "  flashing-furnace."  The  thick  neck  is  first  heated  at  the 
opening,  whence  a  powerful  flame  is  issuing.  Fuel  is  placed  on  the  grating  for  the  purpose  of  warm- 
ing the  piece,  while  the  neck  is  heated  from  the  larger  furnace  through  an  opening  in  the  side. 
As  soon  as  the  neck  is  sufficients  soft,  a  boy  inserts  a  flat  iron  tool  through  the  nose-hole,  to  smooth 
the  roughness  left  in  the  neck  by  breaking  it  off  as  described  above.  When  the  neck  has  been  suffi- 
ciently heated  at  the  nose-hole,  the  bell-shaped  vessel  is  brought  in  front  of  another  opening,  where 
it  receives  the  full  heat  of  the  flame,  and  the  pipe  is  then  made  to  revolve  with  the  greatest  possible 



rapidity.  The  action  of  this  rotary  motion  upon  the  softened  glass  is  easily  conceived.  The  centri- 
fugal force  communicates  to  the  particles  of  glass  a  tendency  to  fly  off  at  a  tangent,  and  to  arrange 
themselves  in  a  circular  plane  perpendicular  to  the  axis  of  rotation.  The  mouth,  being  the  softest 
part,  first  expands,  and  this  quickly  enlarges  until  the  whole  suddenly  opens  into  one  sheet  of  glass, 
Fig.  2174,  about  6  feet  in  diameter,  which,  with  the  exception  of  the  central  portion,  is  of  nearly 




uniform  thickness.  It  is  obvious  that  a  sheet  of  such  dimensions  must  quickly  fold  together  in  the 
soft  state,  if  the  rotary  motion  is  not  kept  up.  The  workman,  therefore,  continues  the  rotation  after 
the  removal  of  the  sheet  from  the  flame  of  the  furnace,  until  it  reaches  the  annealing-oven,  where 
it  is  placed  on  a  small  circular  bench,  and  is  detached  from  the  rod  by  means  of  a  pair  of  strong 
shears,  leaving  a  mark  called  the  "  bullion,"  or  bull's-eye.     Another  workman,  who  has  charge  of 

the  annealing,  now  raises  the"ta- 
£175.  ble"  of  glass  upon  a  large  fork-like 

instrument,  and  carries  it  to  an  up- 
right position  iu  the  annealing-arch, 
Fig.  217").  The  tables  stand  thus 
OD  their  edges,  upon  two  strong  par- 
allel iron  supports,  which  run  the 
whole  length  of  the  annealing-kiln. 
The  glass,  alter  remaining  in  the 
kiln  for  a  considerable  time,  during 
which  the  cooling  has  been  care- 
fully regulated,  is  withdrawn,  so  as 
to  enable  a  workman  to  go  inside 
and  hand  out  each  table  on  the  out- 
side to  an  assistant. 

This  mode  of  manufacture  pos- 
sesses at  present  little  more  than 
retrospective  interest,  despite  the  advantage  which  it  offers  in  the  brilliancy  of  the  glass  produced. 
To  make  a  sheet-glass  in  which  shall  be  united  the  brilliant  qualities  of  crown-glass  with  the  cheap- 
ness of  cylinder-glass  is  one  of  the  most  important  problems  in  glass-making  which  inventors  have 
yet  to  solve. 

Plate- Glass.— The  composition  of  this  glass  is  given  by  Feligot  as  follows: 



St.  Gobain  glass 

Same,  old  make 

Glass  from  two  English  factories  •. 

English  glass,  Ravenhead 

Amelung  glass,  from  Dorpat 
















Alumina  and 
Iron  Oxide. 






The  mixture  used  in  the  leading  glass-houses  of  Europe  is :  white  sand,  300  parts ;  soda  salt  at 
85°  to  90°,  110  to  120;  limestone,50 ;  glass  fragments,  300.  In  some  establishments  the  limestone 
is  replaced  by  45  parts  of  slacked  lime. 

The  building  or  factory  for  the  manufacture  of  plate-glass  is  generally  of  very  large  size.  That  of 
the  British  Plate-Glass  Works  at  Ravenhead,  where  it  is  called  the  foundry,  is  339  feet  long  by  155 
feet  wide;  and  the  famous  halle  of  St.  Gobain  in  France  is  174  by  120  feet.  In  the  centre  is  the 
square  melting-furnace,  with  openings  on  two  parallel  sides  for  working  purposes,  while  along  two 
sides  of  the  great  building  are  arranged  annealing-ovens,  which  are  sometimes  30  by  20  feet  in  order 
to  receive  the  immense  plates  that  are  to  be  annealed.  Two  kinds  of  pots  are  used :  the  ordinary 
one,  open  at  the  top,  for  melting  the  glass ;  and  cisterns  or  cuvettes,  in  which  the  molten  glass  is 
carried  to  the  casting-table.  In  France  the  cuvette  is  usually  of  a  quadrangular  form,  with  a  groove 
in  each  of  its  sides,  or,  as  in  the  case  of  the  larger  cisterns,  in  two  parallel  sides,  in  which  the  tongs 
or  iron  frame  are  fitted  when  the  cuvette  is  moved.  Between  each  two  pots  in  the  furnace  are  placed, 
according  to  their  size,  one  or  more  cuvettes.  In  some  establishments  the  cuvette  is  not  now  used, 
the  metal  being  poured  from  the  pot  in  which  it  is  melted  on  to  the  eastins-table.  In  France  16 
hours  are  allowed  for  the  melting,  and  the  same  time  for  the  metal  to  remain  in  the  cuvettes ;  but 
the  latter  term  is  often  extended  in  order  that  the  aeriform  bubbles  may  escape  and  the  excess  of 
soda  become  volatilized.  Toward  the  last  the  temperature  is  allowed  to  fall,  and  the  glass  then 
acquires  the  slight  degree  of  viscidity  suitable  for  casting.     The  molten  glass  is  transferred  from  the 



pots  into  the  adjacent  cuvettes  by  means  of  wrought-iron  ladles  with  long  handles.  When  the  glass 
is  in  the  proper  condition  to  be  cast,  the  "  tongs  carriage,"  consisting  of  two  powerful  bars  of  iron 
united  like  two  scissors-blades,  and  resting  upon  two  wheels,  is  pushed  into  the  opening  made  in  the 
furnace,  and  the  cuvette  is  clamped  in  the  quadrant  formed  at  the  extremity  of  the  tongs,  two  workmen 
manipulating  the  handles  at  the  other  extremity.  The  cistern,  thus  taken  from  the  furnace  full  of 
molten  glass,  is  placed  on  another  carriage  and  quickly  conveyed  to  the  casting-table,  Fig.  2176. 
This  consists  of  a  massive  slab,  usually  of  cast-iron,  supported  by  a  frame,  and  generally  placed  at 
the  mouth  of  the  annealing-oven.  At  the  Thames  Works  in  England  the  casting-plate  is  20  feet  long, 
1 1  feet  broad,  and  7  inches  thick.  Formerly  these  tables  were  of  bronze,  and  the  great  slab  of  St. 
Gobain  of  this  alloy  weighed  50,000  lbs. ;  but  cast-iron  was  found  less  liable  to  crack,  and  is  now 
generally  used  for  this  purpose.  On  each  side 
of  the  tables  are  ribs  or  bars  of  metal,  which 
keep  the  glass  within  proper  limits,  and  by  their 
height  determine  the  thickness  of  the  plate.  A 
copper  or  bronze  cylinder  about  a  foot  in  diame- 
ter, resting  upon  these  bars,  extends  across  the 
table.  After  being  heated  by  hot  coals  placed 
upon  it,  the  table  is  carefully  cleaned  prepara- 
tory to  casting.  The  cistern  containing  the  melt- 
ed glass  is  raised  from  the  carriage  on  which  it 
was  brought  from  the  furnace  by  means  of  a 
crane,  its  outside  carefully  cleaned,  and  the  glass 
skimmed  with  a  copper  sabre.  The  cuvette  is 
now  swung  round  over  the  table,  over  which  a 
roller  covered  with  cloth  is  drawn  to  remove  all  impurities,  and  the  molten  glass  poured  out  in  front 
of  the  cylinder,  which,  being  rolled  from  one  extremity  of  the  tabic  to  the  other,  spreads  out  the  glass 
in  a  sheet  of  uniform  breadth  and  thickness.  The  operation  is  a  beautiful  one  from  the  brilliancy 
of  the  great  surface  of  melted  glass,  and  the  variety  of  colors  exhibited  upon  it  after  the  passage  of 
the  roller.  While  the  plate  is  still  red-hot  about  2  inches  of  its  end  is  turned  up  like  a  flange,  against 
which  an  iron  rake-like  instrument  is  placed,  and  the  plate  is  thrust  forward  into  the  annealing-oven, 
the  temperature  of  which  is  that  of  dull  redness.  Another  plate  is  now  immediately  cast  upon  the 
hot  table,  and  the  annealing-oven  when  filled  is  closed  and  left  for  about  five  days  to  cool.  The  pro- 
cess of  casting  is  done  so  systematically  and  with  such  dispatch  in  a  well-regulated  establishment, 
that  the  glass  has  been  taken  from  the  furnace,  cast,  and  put  into  the  annealing-oven  in  less  than 
five  minutes.  From  the  annealing-oven  the  plates  are  taken  to  the  warehouse,  where  they  are  care- 
fully examined  to  see  how  they  may  be  cut  to  the  best  advantage. 

In  different  manufactories  and  at  different  times  various  processes  have  been  in  use  for  grinding 
and  smoothing  the  surface  of  plate-glass,  but  the  principle  has  been  the  same  in  all,  viz. :  rubbing 
the  surface  to  be  smoothed  with  another  surface  either  of  glass  or  iron,  and  at  the  same  time  apply- 
ing sand  or  emery  of  different  degrees  of  fineness  and  water  between  the  two  impinging  surfaces. 
One  of  the  most  approved  methods  of  grinding  and  smoothing  the  plates  was  introduced  into  Eng- 
land in  1856,  and  adopted  in  the  British  Plate-Glass  Works.  This  apparatus  consists  of  a  revolving 
table,  20  feet  in  diameter,  fixed  upon  a  strong  cast-iron  spindle,  and  capable  of  running  at  an  aver- 
age speed  of  25  revolutions  a  minute.  Above  the  table  frames  are  arranged  to  hold  the  plates  of 
glass,  which  are  laid  in  a  bed  of  plaster  of  Paris,  with  the  face  to  be  polished  resting  upon  the  table. 
These  frames  also  revolve  on  their  centres  by  the  friction  of  the  table  upon  the  glass,  slowly,  but  so 
as  to  present  each  side  of  the  plates  they  hold  to  an  equal  amount  of  rubbing  as  they  are  moved 
nearer  to  the  centre  of  the  table  or  farther  from  it.  Sand  and  water  are  applied  to  facilitate  grind- 
ing down  the  glass.  The  grinding  by  this  process  is  found  to  be  even  and  equal,  and  the  machinery 
to  work  smoothly  and  steadily  from  the  facility  with  which  the  plates  accommodate  themselves  to  the 
power  applied.  After  grinding  they  are  smoothed  with  emery  powder  of  finer  and  finer  qualities,  and 
are  thus  prepared  for  polishing.  By  the  process  above  described  the  grinding  and  smoothing  are  done 
by  the  same  machine ;  but  formerly  two  sets  of  apparatus  were  required  for  this  purpose.  By  grind- 
ing, the  surface  of  the  plate  is  made  true,  but  presents  a  rough  appearance  which  is  removed  by  the 
process  of  smoothing.  At  this  stage  it  is  somewhat  opaque,  but  this  defect  disappears  after  the  final 
process  of  polishing.  This  is  performed  chiefly  by  machinery.  The  plate  of  glass  having  been  fixed 
upon  the  table  by  means  of  plaster  of  Paris,  the  surface  is  subjected  to  the  action  of  a  series  of 
wooden  blocks  covered  with  felt  and  attached  to  a  frame  by  which  they  are  made  to  move  over  the 
surface  of  the  glass.  At  the  same  time  a  polishing  powder,  generally  red  oxide  of  iron,  is  applied, 
while  the  friclion  may  be  increased  by  adding  weight  to  the  rubbers.  Polishing  sometimes  brings 
out  defects  which  were  before  concealed ;  the  plates  are  consequently  again  assorted,  and,  if  need 
be,  reduced  to  smaller  sizes.  Bending  the  large  plates  or  the  smaller  sheets  of  glass  for  the  purpose 
of  fitting  them  for  bow  windows,  etc.,  is  an  especial  branch  of  the  manufacture.  A  core  of  refrac- 
tory material  and  suitable  shape  is  introduced  upon  the  floor  of  the  furnace ;  and  upon  this  is  laid 
the  sheet  to  be  bent,  which  as  it  softens  by  gravity  conforms  itself  to  the  shape  of  the  bed  upon 
which  it  is  laid. 

The  value  of  plate-glass  varies  greatly  with  the  size.  In  the  United  States  the  price  of  a  plate  of 
standard  British  or  French  glass,  5x3  feet,  is  about  -$35 ;  but  when  the  dimensions  are  double,  the 
plate  being  10  x  6  feet,  the  price  is  increased  to  about  $175.  A  plate  14  x  8  feet  is  valued  at  about 

In  Bessemer's  method  of  casting  plate-glass,  a  reverberatory  furnace  is  employed,  Fig.  2177,  with  a 
low  arch  and  descending  flue  d.  The  flame,  proceeding  from  the  grate  a,  plays  upon  the  surface  of 
the  materials  in  the  pot  e,  in  the  fire-space  b.     The  arch  is  formed  at  that  part  which  is  most  exposed 



to  the  heat  and  the  alkaline  vapors  from  the  mixture,  of  hollow  bricks  ccc,  over  which  a  draught 
of  cold  air  is  caused  to  play  by  connecting  the  space  above  the  furnace  with  the  ascending  main 
chimney.  The  object  of  this  cooling,  which  is  of  course  attended  with  a  loss  of  heat,  is  to  prevent 
tears,  consisting  of  the  fusible  product  of  the  action  of  the  alkaline  vapors  upon  the  ingredients  of 
the  bricks,  from  forming  on  the  arch,  and  falling  into  the  glass  during  fusion.  The  pot,  e,  is  of  very 
large  dimensions,  as  large  indeed  at  the  lip  on  the  one  side  as  the  width  of  the  plates  which  it  is 
proposed  to  cast  with  it.  It  is  set  upon  a  siege  composed  of  large  masses  of  fire-stone,  and  these 
are  cemented  together,  as  well  as  the  pot  upon  them,  by  some  bottle-glass,  which,  in  the  fused  state, 
enters  the  crevices  and  binds  the  whole  firmly  together  upon  the  strong-ribbed  cast-iron  frame  g. 

This  frame  moves  upon  four  wheels  h  on  a  railway  to,  which  extends  beyond  the  furnace  to  the 
rolling  machinery,  to  be  described  immediately.  Thus  pot,  Biege,  and  frame  arc  all  wheeled  in  and 
out  of  the  furnace  at  once,  as  will  be  seen  by  reference  to  the  section,  Fig.  2178,  where  i  j  represent 
the  hollow  brick,  or  masses  of  stone,  by  the  removal  of  which  a  free  ingress  and  egress  is  allowed 
the  whole  carriage  on  the  continuation  of  the  rail.  The  pot  and  carriage  fill  the  entire  recess  in  the 
furnace,  and  the  flame  playing  upon  the  top  does  not  much  affect  the  iron  frame  of  the  carriage 
through  the  bad  conducting-stones  which  form  the  bed  of  the  pot.  Fig.  2179  is  a  longitudinal  sec- 
tion through  the  middle  of  the  framework  and  machinery,  by  moans  of  which  the  pot  and  siege  are 
raised,  and  the  melted  glass  poured  out  between  the  rollers.  It  shows  the  pot  in  an  elevated  position 
and  partly  emptied. 

The  mode  of  operating  with  this  apparatus  is  as  follows  :  When  the  glass  is  in  a  fit  state  for  cast- 
ing, the  door  is  removed  by  a  crane  from  the  mouth  of  the  furnace,  and  by  the  assistance  of  an  iron 

hook  the  carriage  and  its  pot  are  easily 
rolled  forward  upon  the  rails  before  men- 
tioned to  the  tilting-frame  t.  The  carriage 
and  its  pot  are  now  moved  forward  until 
the  set-screws  M  come  in  contact  with  the 
carriage;  the  office  of  these  screws  is  to 
regulate  the  extent  to  which  the  lip  of  the 
pot  shall  overhang  the  roller  r/,  so  that 
when  a  new  pot  is  used  its  proper  position 
for  pouring  may  be  adjusted.  The  screws 
M  pass  through  stout  lugs  N,  cast  on  the 
piece  u  ;  the  handle  on  X  being  turned, 
the  pot  will  be  elevated,  as  shown  in  Fig. 
2 !  79,  when  the  glass  passing  between  the 
rollers  will  be  formed  into  sheets.  When 
the  pot  is  emptied  it  is  again  lowered  and 
returned  to  the  furnace  for  a  repetition  of 
the  preceding  operations.  The  roller  f  is 
furnished  with  a  longitudinal  rib,  which 
at  each  revolution  cuts  the  glass  off  into 

Flint-Glass. — The  best  flint-glass  is  subject  to  defects,  chief  among  which  are  undulatorv  appear- 
ances called  strice,  resulting  from  a  want  of  uniform  density  in  the  glass,  and  tending  to  refract  and 
disperse  in  different  directions  the  rays  of  light  passing  through  it.  These  defects  are  of  great  im- 
portance when  the  glass  is  to  be  used  for  optical  purposes.  In  1753  John  Dollond,  an  English 
optician,  first  began  the  construction  of  achromatic  object-glasses,  formed  of  two  kinds  of  glass 
of  different  density;  for  this  purpose  he  used  fragments  of  flint-  and  of  crown-glass,  but  did  not 
succeed  in  making  object-glasses  with  a  larger  aperture  than  2  or  3  inches  in  diameter ;  and  when 
the  need  of  telescopes  of  greater  magnifying  power  was  strongly  felt,  it  was  difficult  to  produce  flint- 
glass  sufficiently  free  from  strife  for  a  lens  4  inches  in  diameter.  The  invention  of  a  means  of  pro- 
ducing flint-glass  free  from  striae  was  made  by  M.  Guinand  of  Brennets,  Switzerland,  and  it  consisted 



in  working  and  stirring  the  material  while  in  a  state  of  fusion,  by  means  of  a  tool  made  of  the  same 
material  as  the  crucible  or  glass-pot.  He  made  a  hollow  cylinder  of  fire-clay  of  the  same  height  as 
the  crucible,  closed  at  its  lower  extremity  and  open  above,  with  a  flat  ledge  all  round  of  several 
centimetres  in  width.  Having  heated  this  cylinder  red-hot,  he  placed  it  in  the  melted  glass ;  then, 
by  means  of  a  long  bar  of  iron,  bent  to  a  right  angle  at  a  distance  of  some  centimetres  from  its 
extremity,  which  he  introduced  into  the  cylinder  of  fire-clay,  he  worked  and  stirred  the  glass,  by 

giving  the  bar  a  horizontal  rotary  motion.  For  the  manufacture  of  flint-glass,  and  of  crown-glass, 
he  adopted  a  circular  furnace,  in  the  centre  of  which  is  placed  the  crucible  or  glass-pot,  all  the  parts 
of  which  are  exposed  to  the  same  temperature ;  and  covered  crucibles  are  adopted,  because  with 
crucibles  of  this  form  there  is  no  danger  of  the  glass  being  spoiled  by  particles  of  the  fuel,  or  by 
drops  or  tears  from  the  crown  or  arch  of  the  furnace.  For  the  construction  of  this,  sec  Furnaces, 

Flint-glass,  of  the  usual  density,  similar  to  that  used  for  table-sets,  decanters,  etc.,  is  composed, 
ordinarily,  of  300  parts  of  sand,  200  of  deutoxide  of  lead,  and  100  of  subcarbonate  of  potash.  The 
density  of  this  flint-glass  is  from  3.1  to  3.2.  The  following  composition,  expressed  in  kilogrammes, 
gives  the  quantity  necessary  to  fill  the  crucible :  sand,  100  kilogrammes ;  deutoxide  of  lead,  100 
kilogrammes  ;  subcarbonate  of  potash,  30  kilogrammes.  This  composition  gives  a  very  white  flint- 
glass,  of  a  density  of  from  3.5  to  3.6,  and  which  is  perfectly  suitable  for  opticians. 

The  details  of  the  operation  are  as  follows :  The  crucible  is  to  be  heated  in  a  special  furnace  kept 
for  the  purpose,  and  when  at  a  white  heat  it  is  to  be  introduced  in  the  usual  manner  into  the  melt- 
ing-furnace, which  has  been  brought  to  the  same  temperature.  This  operation  cools  the  furnace  and 
the  crucible.  The  furnace  must  be  reheated  in  order  to  bring  it  to  the  highest  possible  temperature 
before  introducing  the  materials.  This  takes  about  three  hours.  The  throat  of  the  crucible,  which 
has  been  closed  with  two  stoppers  to  prevent  the  entrance  of  smoke,  is  then  opened,  and  about  10 
kilogrammes  introduced ;  one  hour  after,  about  20  kilogrammes  more ;  then,  two  hours  after,  40 
kilogrammes.  Each  time  the  crucible  must  be  reclosed  with  the  greatest  care,  and  nothing  must  be 
put  in  until  the  coal  on  the  grate  ceases  to  give  out  any  smoke.  At  the  end  of  from  8  to  10  hours 
the  whole  of  the  composition  will  have  been  introduced.  The  crucible  is  left  without  being  opened 
for  about  4  hours ;  then  the  stoppers  are  removed  for  the  purpose  of  introducing  the  cylinder  of  fire- 
clay, which  has  been  heated  separately  to  a  white  heat  in  the  same  furnace,  and  kept  at  that  tem- 
perature until  placed  in  the  crucible ;  care  is  to  be  taken  to  keep  it  perfectly  clean  and  free  from 
ashes.  At  this  period  the  flint-glass  is  melted,  but  it  still  contains  bubbles.  Nevertheless,  the  bent 
iron  bar  is  introduced  into  the  cylinder,  and  the  first  stirring  is  given,  which  serves  to  coat  the  cylin- 
der with  glass,  and  to  effect  a  more  intimate  mixture.  In  about  3  minutes  the  iron  bar  is  white-hot ; 
it  is  taken  out,  and  the  ledge  of  the  cylinder  is  placed  on  the  edge  of  the  crucible.  This  cylinder, 
being  specifically  lighter  than  the  glass,  floats  slightly  inclined,  because  its  upper  ledge  is  outside 
of  the  glass.  The  two  stoppers  are  so  replaced  as  not  to  push  the  ledge  of  the  cylinder  into  the 
glass,  and  the  stirring  up  of  the  fire  is  recommenced.  Five  hours  afterward  a  fresh  stirring  up  with 
a  single  iron  bar  takes  place,  the  glass  is  already  well  refined,  and  then  from  hour  to  hour  there  is  a 
stirring,  each  time  with  a  single  iron  bar;  great  care  being  taken  that  at  each  stirring  there^ shall  be 
no  smoke  in  the  furnace,  and  that  the  lower  doors  of  the  furnace  are  closed.  After  haying  thus 
used  6  iron  bars,  from  25  to  30  centimetres  in  thickness  of  coal  is  thrown  on  the  grate,  which  forms 
a  mass  quickly  reduced  to  coke,  and  which  allows  the  furnace  to  cool  without  exposing  the  grate 



uncovered.  The  various  openings  of  the  furnace  are  unclosed ;  the  whole  furnace  and  the  crucible 
thus  gradually  and  slowly  cool.  This  operation  tends  to  cause  the  bubbles  which  are  not  yet  dis- 
engaged to  rise  to  the  surface.  At  the  end  of  two  hours  this  operation  is  finished,  and  the  furnace 
is  again  brought  to  the  melting  heat.  Alter  five  hours  of  the  highest  temperature,  the  glass  has  re- 
sumed its  greatest  fluidity,  the  bubbles  have  disappeared,  the  grates  are  completely  closed  below, 
and  the  great  stirring  {brassage)  commences;  that  is  to  say,  as  soon  as  one  iron  bar  is  hot,  another 
is  substituted  for  it,  and  so  on  for  about  two  hours.  At  the  end  of  this  time  the  material  has 
acquired  a  certain  consistence,  and  the  stirring  is  not  executed  without  difficulty;  then  the  last  iron 
bar  is  taken  out,  and  the  cylinder  is  removed  from  the  crucible,  which  is  very  carefully  closed,  as 
well  as  the  chimneys  and  openings,  except  a  small  hole  of  two  centimetres  to  permit  the  escape  of 
the  gas  which  may  have  remained  in  the  fuel.  When  the  disengagement  of  gas  ceases,  the  furnace 
is  entirely  closed,  ami  it  is  suffered  to  cool,  which  takes  about  8  days.  The  door  of  the  furnace  is 
then  removed,  and  the  crucible  with  its  contents  taken  out,  usually  in  a  single  mass,  except  some 
fragments  which  become  detached  round  it.  The  only  object  now  is  to  make  use  of  this  mass  and 
these  fragments,  the  mode  of  doing  which  we  will  explain  directly,  alter  having  given  the  details  of 
the  operation  for  crown-glass,  which,  as  may  be  supposed,  has  a  great  analogy  with  the  preceding. 

Manufacture  of  Crown- Glass. — After  many  experiments,  the  following  composition  is  found  to  be 
the  best:  white  sand,  120  kilogrammes;  subcarbonate  of  potash,  85  kilogrammes;  subcarbonatc  of 
soda,  2u  kilogrammes;  chalk,  L5  kilogrammes;  arsenic,  1  kilogramme. 

The  crucible  having  been  placed  in  the  furnace,  as  for  flint-glass,  the  introduction  of  all  the 
materials  is  to  be  completed  in  about  8  hours,  4  or  5  hours  alter  which  the  cylinder  is  to  be  intro- 
duced, and  the  first  stirring  takes  place  ;  then,  every  2  hours,  a  stirring  with  a  simile  iron  bar;  G  are 
to  be  executed  in  this  way.  The  furnace  is  to  cool  very  slowly  for  2  hours,  after  which  it  is  to  be 
reheated  for  7  hours,  this  glass  regaining  its  heat  with  much  more  difficulty  than  flint-glass.  The 
great  stirring  then  takes  place,  which  lasts  about  an  hour  and  a  quarter.  The  crucible,  the  chimneys, 
and  the  openings  are  closed  as  for  flint-glass,  and  the  whole  is  left  to  cool.  Parallel  faces  are  made 
on  the  sides  of  the  mass,  whether  of  flint-  or  crown-glass,  in  order  to  examine  the  interior  to  deter- 
mine the  mode  of  division.  It  is  then  sawed  into  slices.  Faces  arc  also  polished  on  the  fragments 
for  the  purpose  of  examining  them,  and  disks  are  made  of  thnu  in  accordance  with  their  weight. 
For  this  purpose,  they  are  first  heated  in  a  furnace  and  then  introduced  into  a  muffle,  where  only  the 
heat  necessary  to  mould  them  is  given.  If  the  fragment  is  irregular,  it  is  partially  rounded  by  the 
nippers  and  then  moulded  in  a  press,  after  which  it  is  annealed. 

Crystal. — This  glass  is  sometimes  termed  tlint-;_rla>s  in  England.  It  is  chiefly  notable  as  contain- 
ing lead,  the  presence  of  which  renders  the  glass  more  fusible  and  of  higher  refracting  power,  while 
giving  to  it  a  special  sonority  which  renders  it  easily  distinguishable.  The  following  table  shows  the 
composition  of  various  kinds  of  crj  stal  glass,  according  to  Peligot : 



Oxide  of 

Pota  h. 



Oxide  of 

Oxide  of 




M   1 

54.  a 











■  • 









English  crystal  (Faraday's  analysis). 

In  large  French  establishments  the  usual  composition  of  crystal  is :  sand,  300  parts  ;  minium, 
240  to  250  ;  potash,  190  to  200.  In  England  the  following  composition  is  used  :  sand,  300;  minium, 
150  to  180;  potash,  220  to  270.  For  the  manufacture  of  this  glass  into  various  objects,  see  Glass- 
wake,  Manufacture  of. 

Demi- Crystal. — This  is  a  variety  of  glass  largely  used  for  vials,  flasks,  and  cheap  tableware. 
Peligot,  among  various  compositions,  gives  the  following  :  sand  well  washed,  300  parts;  soda,  puri- 
fied and  Imitated,  from  55°  to  60°,  130  parts;  slacked  lime,  50  parts. 

Bohemian  Class. — This  celebrated  glass  is  almost  as  cheap  as  demi-crystal,  while  it  is  as  brilliant 
and  homogeneous  as  crystal  itself.     Peligot  gives  the  following  analyses  of  three  samples : 





Alumina  and 
Oxide  of  Iron. 










The  following  is  the  composition  used  at  the  glass-works  near  Gratzen,  Bohemia:  pulverized 
quartz,  100  parts ;  slacked  lime,  17 ;  carbonate  of  potash,  32  ;  oxide  of  manganese,  1 ;  white  arsenic, 
3  ;  together  with  from  one-third  to  one-half  the  weight  of  the  foregoing  composition  in  glass  scrap. 

Slaa-Glass. — The  use  of  blast-furnace  slag  for  the  manufacture  of  glass  has  been  proposed  by  Mr. 
Bashley  Britten  (sec  Engineering,  xxii.,  283)7  The  slag  is  run  directly  into  Siemens  furnaces.  Two 
of  these  furnaces  are  so  provided  that  they  can  be  rclined  or  repaired  alternately  without  stopping 
■work.  In  working,  these  converting  tanks  are  kept  supplied  with  silica  in  excess ;  this  may  be  in  the 
usual  form  of  sand,  but  flints,  coarse  sifted  gravel,  or  fragments  of  quartz  or  any  other  silicious 
stone,  are  to  be  preferred  when  readily  obtainable,  as  they  form  a  more  permeable  mass,  and  are 
readily  dissolved  in  contact  with  the  basic  slag.     It  is  convenient  that  the  fresh  supplies  of  silica 


should  be  introduced  when  no  slag  is  running,  in  order  that  it  may  become  heated  in  the  interval  to 
avoid  chilling  the  slag  when  it  is  admitted ;  as  the  slag  is  introduced  it  is  fed  by  a  hopper  or  other 
means  with  the  alkali.  No  stirring  or  mechanical  agitation  is  needed,  as  the  ingredients  mingle  of 
themselves ;  and,  as  thev  combine  and  become  glass,  this,  being  of  a  denser  nature  than  the  crude 
materials,  sinks  below  them  and  forms  a  substratum  of  clear  glass,  with  the  yet  imperfect  glass  and 
undissolved  silica  floating  on  its  surface.  The  clear  glass,  as  it  is  wanted,  is  tapped  from  the  bottom 
of  the  tank,  and  received  in  a  ladle  holding  a  ton  or  more.  This  ladle  is  lifted  by  a  crane,  and  is 
drawn  along  a  tramway  to  the  glass-house,  situate  as  near  as  circumstances  permit ;  when  brought 
opposite  to  the  opening  at  the  back  of  the  working-out  furnaces,  the  ladle  is  tilted  on  its  trunnions, 
and  the  glass  is  poured  into  the  tank  by  a  spout.  The  glass  can  then  be  used  at  once  as  it  is,  or  its 
color  or  other  quality  may  be  changed  by  adding  to  it  what  is  needed  for  that  purpose. 

The  Bastie  Toughened  Glass.— By  the  process  of  tempering  devised  by  M.  de  la  Bastie,  the  hard- 
ness of  "lass  is  very  much  increased.  The  operation  consists  in  immersing  the  hot  glass  in  a  bath 
of  oils,  grease,  wax,  or  resinous  substance,  the  temperature  of  which  is  above  that  of  boiling  water. 
Hardened  glass  will  stand  blows  of  about  double  the  energy  of  those  which  will  shatter  ordinary 
glass  of  similar  thickness.  Its  resistance  to  shearing  stress  is  about  three  times  that  of  common 
glass.  On  rupture,  however,  it  disaggregates.  It  may  be  etched  with  hydrofluoric  acid,  or  engraved 
with  the  sand-blast,  without  becoming  impaired  in  point  of  strength.  It  cannot^  be  cut  with  a  dia- 
mond, as  the  removal  of  a  portion  determines  the  rupture  of  the  entire  piece.  It  is  in  use  for  photo- 
graphic negatives,  articles  of  table  furniture,  and  lamp-chimneys,  and  has  withstood  the  action  of  a 
cupel  furnace  at  white  heat  for  several  davs.  The  furnaces  used  by  M.  de  la  Bastie  are  described 
under  Furnaces,  Glass.  (See  Popular  Science  Monthly,  vii.,  558.  For  tests  of  tempered  glass,  see 
Scientific  American,  xxxii.,  402.) 

Colored  and  Ornamented  Glass.— Colored  glass  is  produced  either  upon  strass  for  imitations  of 
precious  stones,  or  by  introducing  the  various  oxides  used  for  coloring  into  the  materials  of  flint  or 
other  kinds  of  glass.  In  the  latter  case  the  coloring  matter  is  thoroughly  fused  with  the  glass,  which 
therefore  becomes  colored  throughout  its  entire  body.  Pigments  are  also  applied  to  the  surface  of 
glass,  and  sometimes  by  their  greater  fusibility  are  burnt  or  melted  in.  Flint-glass  may  be  employed 
for  vessels  ornamented  with  colors,  and  to  6  cwt.  of  it  the  following  ingredients  are  added  for  produc- 
ing the  respective  colors:  soft  white  enamel,  24  lbs.  arsenic,  6  lbs.  antimony;  hard  white  enamel, 
200  lbs.  putty,  prepared  from  tin  and  lead ;  blue  transparent  glass,  2  lbs.  oxide  of  cobalt ;  azure- 
blue,  about  6  lbs.  oxide  of  copper ;  ruby-red,  4  oz.  oxide  of  gold  ;  amethyst  or  purple,  20  lbs.  oxide 
of  manganese-,  common  orange,  12  lbs.  iron  ore  and  4  lbs.  manganese;  emerald-green,  12  lbs.  cop- 
per scales  and  12  lbs.  iron  ore  ;  gold  topaz  color,  3  lbs.  oxide  of  uranium.  The  colors  produced  by 
the  metallic  oxides  are  found  to  varv  with  the  degree  of  heat  employed.  All  the  colors  of  the  spec- 
trum may  be  obtained  with  oxide  of  iron ;  and  these  various  effects  do  not  seem  to  depend  upon  the 
different  decrees  of  oxidation,  but  are  thought  to  result  from  variations  in  molecular  arrangement, 
induced  perhaps  by  the  action  of  light.  By  another  process  the  surface  alone  of  the  glass  may  be 
colored.  This  is  done  by  first  gathering  with  the  blowpipe  a  lump  of  clear  glass,  which  after  being 
rolled  upon  the  marver  is  dipped  into  a  pot  of  melted  colored  glass,  forming  a  lump  of  colorless 
glass  enveloped  in  a  coating  of  colored  glass.  This  is  blown  into  a  globe  or  cylinder  and  opened  out 
into  a  sheet  or  plate  in  the  usual  manner,  one  surface  of  which  is  clear  and  the  other  colored.  Ves- 
sels of  various  kinds  having  colored  surfaces  on  the  outside  may  be  produced  in  a  similar  manner. 
By  cutting  through  the  thin  layer  of  colored  glass  to  the  colorless  layer,  a  great  variety  of  colored 
ornamental  glass  may  be  produced.  By  gathering  first  a  lump  of  colored  glass  and  then  coating  this 
with  melted  clear  u'lass.  the  external  surface  of  the  vessel  will  be  colorless  and  the  inner  layer 
colored.  "  Casing  "  is  a  somewhat  similar  process.  The  article  of  flint-glass  when  partially  blown 
is  inserted  into  a  thin  shell  of  colored  glass,  prepared  at  the  same  time  for  its  reception,  and  the 
blowing  is  continued  till  the  inner  one  fills  the  shell,  with  which  it  is  afterward  well  incorporated  by 
softening  in  the  furnace  and  further  blowing.  Several  partial  casings  of  different  colors  may  be 
thus  applied.  , 

In  making  etched  enameled  sjlass,  the  enamel  substance  is  ground  to  an  impalpable  powder,  and 
laid  with  a  brush  in  a  pasty  state  upon  the  glass.  After  the  paste  is  dried,  the  ornament  is  etched 
out  by  machinery  or  by  hand,  and  the  glass  is  then  softened  till  the  enamel  is  vitrified  and  incorpora- 
ted with  it.  From  this  it  is  removed  to  the  annealing-kiln.  The  flocked  variety  of  enameled  glass 
is  prepared  by  the  same  method,  except  that  a  fine,  smooth,  opaque  surface,  like  satin,  much  softer 
and  smoother  than  that  of  ground  glass,  is  previously  given  to  the  whole  surface  before  the  enamel 
is  applied.  This  variety  has  in  great  part  supplanted  the  other,  and  is  justly  much  admired  lor  the 
softening  of  the  light  diffused  through  it,  and  for  the  delicacy  and  beauty  of  the  elaborate  and  artis- 
tic designs  with  which  it  is  ornamented.  u        . 

Works  for  Reference.— Among  the  most  valuable  treatises  on  the  subject  of  glass  are  Curiosities 
of  Glass-Making,"  by  Apsley  Pellatt  (London,  1849),  and  "  Guide  du  Verrier,"  by  G  Lontemps 
(Paris,  1S68),  both  of  these  authors  having  been  for  many  years  extensively  engaged  in  the  manufac- 
ture of  glass.  Among  other  works  are  those  of  Neri,  "  The  Art  of  Glass  "  (translated,  London, 
1662);  Shaw,  "The  Chemistrv  of  Porcelain,  Glass,  and  Pottery"  (London,  1837);  Henry  Chance 
"On  the  Manufacture  of  Crown  and  Sheet  Glass,"  London,  1856,  and  "On  the  Manufacture  ot 
Glass,"  1868;  Peligot,  "  L'Art  de  la  Verrerie,"  Paris,  1862;  Turgan,  "  Les  grandes  L  sines  de 
France"  Paris,  lS62-'70;  Cochin,  " La  Manufacture  des  Glaces  de  Saint-Gobain  de  166o  a  lhbo 
Paris,  1365;  Gaffield,  "Action  of  Sunlight  on  Glass,"  reprinted  from  the  "American  Journal  ot 
Science  and  Arts,"  New  Haven,  1867  ;  Sauzay,  "  La  Verrerie,"  Paris,  1868,  and  "W  onders  of  Glass- 
Making  in  all  Ages,"  London  and  New  York,  1870;  and  "Kapports  du  Jury  International  _  ot  tne 
Paris  Universal  Exposition  of  1867,  vol.  cxi.  (Paris,  1868).  See  also  "Le  Verre,  son  Histoire  et  sa 
Fabrication,"  Peligot,  Paris,  1877. 



GLASS,  ORNAMENTATION  OF.  The  Venetians  and  Bohemians  have  long  been  celebrated  for 
their  skill  and  ingenuity  in  the  production  of  ornamented  glass.  Examples  of  their  handiwork  are 
given  in  Eigs.  2180  and  2181,  Fig.  21. so  representing  a  Venetian  bottle,  and  Fig.  2181  a  Bohemian 
drinking-glass.  Many  ingenious  effects  produced  are  imitations  of  ancient  manufacture,  of  which 
many  wonderful  specimens  are  preserved  in  European  museums.  The  process  of  drawing  out  tubes 
is  an  interesting  one.  The  workman,  having  gathered  a  lump  of  glass  on  the  end  of  a  blow-pipe,  ex- 
pands it  into  a  globular  form  with  very  thick  walls.  Another  workman  having  attached  a  punty  to  the 
opposite  end,  the  two  men  separate  from  each  other  as  quickly  as  possible,  thus  elongating  the  glass 
into  a  tube.  The  globe  immediately  contracts  across  the  centre,  which,  being  drawn  out  to  the  size  of 
the  tube  desired,  cools,  so  that  the  hotter  and  softer  portions  next  yield  in  their  dimensions,  and  so  on 
until  a  tube  of  100  feet  or  more  hangs  between  the  men.  It  is  kept  constantly  rotating  in  the  hands, 
and  is  straightened  as  it  cools  and  sets  by  placing  it  on  the  ground.  It  is  cut  into  suitable  lengths 
while  hot  by  taking  hold  of  it  with  cold  tongs.  The  diameter  of  the  bore  retains  its  proportion  to  the 
thickness  of  the  glass ;  hence  thin  tubes  must  be  drawn 
from  globes  blown  to  large  size,  or  from  small  ones 
containing  very  little  metal.  In  producing  canes  the 
glass  is  drawn  out  without  being  blown.  Tubes  thus 
drawn  out  from  colored  glass  are  converted  into  beads 
by  other  curious  processes.  This  branch  of  the  man- 
ufacture is  extensively  practised  at  Murano.     The 



tubes  are  drawn  out  150  feet  in  length,  and  to  the  diameter  of  a  goose-cpiill,  those  for  the  smallest 
beads  by  the  workmen  receding  from  each  other  at  a  pretty  rapid  trot.  The  tubes  are  cut  into 
lengths  of  about  27  inches  and  assorted  for  size  and  color.  Women  or  boys  then  take  several 
together  in  the  left  hand,  and  run  them  on  the  face  of  an  anvil  up  to  a  certain  measure,  and  with  a 
blunt  steel  edge  break  off  the  ends  all  of  the  same  length,  which  is  commonly  about  twice  the  diam- 
eter of  the  tubes ;  the  bits  fall  into  a  box.  These  are  next  worked  about  in  a  moistened  mixture  of 
wood-ashes  and  sand,  with  which  the  cylindrical  pieces  become  filled ;  and  they  are  then  introduced 
with  more  sand  into  a  hollow  cylindrical  vessel,  which  is  placed  in  a  furnace  and  made  to  revolve. 
The  glass  softens,  but  the  paste  within  the  bits  prevents  their  sides  from  being  compressed ;  they 
become  spherical,  and  their  edges  are  smoothed  and  polished  by  the  friction.  "When  taken  from  the 
fire  and  cleaned  from  the  sand,  they  are  ready  to  be  put  up  for  the  market. 

The  Venetian  filigree  glass,  which  consists  of  spirally-twisted  white  and  colored  enamel  glasses 
cased  in  transparent  glass,  is  much  used  for  the  stems  of  wine-glasses,  goblets,  etc. :  and  when  ar- 
ranged side  by  side  in  alternate  colors,  it  is  manufactured  into  tazzas,  vases,  and  other  ornamental 




articles.  In  making  this  kind  of  glass,  pieces  of  plain,  colored,  or  opaque  white  cane,  of  uniform 
length,  are  arranged  on  end,  the  different  colors  alternating,  around  the  interior  of  a  cylindrical 
mould  (Fig.  2182).  The  selection  and  arrangement  of  colors  depend  upon  the  taste  of  the  manufac- 
turer. The  mould  and  the  pieces  having  been  subjected  to  a  moderate  heat,  a  solid  ball  of  trans- 
parent flint-glass,  attached  to  the  end  of  a  blow-pipe  or  punty,  is  placed  within  the  mould,  the  vari- 
ous canes  forming  an  external  coating  to  the  glass,  to  which  they  become  welded.  The  ball  is  now 
taken  from  the  mould,  reheated,  and  marvered  till 
the  adhering  canes  are  rolled  into  one  uniform  mass. 
This  being  covered  with  a  gathering  of  clear  glass, 
the  lumps  thus  formed,  with  the  ornamental  work 
in  the  interior,  may  be  drawn  into  canes  of  any  size, 
and  presenting  either  the  natural  or  the  spiral  ar- 
rangement, the  latter  being  effected  by  the  work- 
men rotating  the  glass  in  opposite  directions  while 
drawing  it  out  into  a  cane.  By  variously  arranging 
the  colors  in  this  process,  and  by  skillful  manipu- 
lations, many  wonderful  and  ingenious  effects  are 
produced.  Beautiful  vases  are  also  made  by  the 
above  process,  the  glass  when  prepared  being  blown 
into  that  form  instead  of  being  drawn  into  canes. 
The  mitte-Jiori  consists  of  a  variety  of  ends  of  va- 
riously-colored tubes,  cut  in  the  form  of  lozenges, 

which,  having  been  arranged  to  represent  flowers  or  other  ornamental  design,  are  enveloped  and 
massed  together  with  transparent  glass.  The  lump  is  then  worked  into  the  required  form,  a  very 
common  one  being  hemispherical  for  use  as  paper  weights.  Portraits  and  even  watches  and  barome- 
ters have  been  represented  in  the  interior  of  glass ;  but  in  this  case  these  articles  and  the  glass  have 
not  formed  a  homogeneous  mass,  the  former  being  arranged  in  a  cavity  of  the  latter. 

Mosaic  glass  is  produced  by  arranging  vertically  side  by  side  threads  or  small  canes  of  variously- 
colored  opaque  or  transparent  glass,  of  uniform  lengths,  so  that  the  ends  shall  form  a  ground  repre- 
senting flowers,  arabesques,  or  any  mosaic  design.  This  mass  is  now  submitted  to  a  heat  sufficient 
to  fuse  the  whole,  all  the  sides  at  the  same  time  being  pressed  together  so  as  to  exclude  the  air  from 
the  interstices  of  the  threads.  The  result  is  a  homogeneous  solid  cane  or  cylinder,  which,  being  cut 
at  right  angles  or  laterally,  yields  a  number  of  layers  or  copies  of  the  same  uniform  design.  This 
process  was  practised  with  great  skill  by  the  ancients,  who  are  supposed  to  have  produced  pictures  in 
this  way ;  but  in  existing  specimens,  the  pieces  have  been  so  accurately  united,  by  intense  heat  or 
otherwise,  that  the  junctures  cannot  even  be  discovered  by  a  powerful  magnifying  glass. 

Vitro  di  trino  represents  fine  lace-work  with  intersecting  lines  of  white  enamel  or  transparent 
glass,  forming  a  series  of  diamond-shaped  sections,  each  containing  an  air-bubble  of  uniform  size. 
In  making  this,  a  lump  of  glass  is  blown  in  a  mould,  around  the  inner  sides  of  which  are  arranged 
pieces  of  canes  of  the  required  colors,  as  described  in  the  case  of  filigree  glass,  which,  adhering  to 
the  glass,  form  ribs  or  flutes  on  its  external  surface.  The  lump,  having  been  twisted  to  give  the 
spiral  arrangement  to  the  adhering  canes,  is  formed  into  a  conical  shape  and  opened  at  the  base. 
This  forms  the  inner  case  of  the  vitro  di  trino.  A  corresponding  outer  case  is  formed  in  the  same 
manner,  which  being  turned  inside  out,  the  projecting  canes  appear  on  the  inside  of  the  cup  with  a 
reversed  spiral  arrangement.  One  case  is  now  placed  within  the  other,  and  both  being  reheated  are 
collapsed  together,  forming  uniform  air-bubbles  between  each  white  enamel-crossed  section.  The 
two  cases,  thus  welded  into  one,  may  be  formed  into  the  bowl  of  a  wine-glass  or  other  vessel. 

Frosted  glass,  like  the  preceding,  is  one  of  the  few  specimens  of  Venetian  work  not  made  by  the 
ancients  ;  and  although  the  process  of  making  it  is  exceedingly  simple,  it  was  considered  a  lost  art 
until  recently  practised  at  the  Falcon  Glass  Works  in  England.  The  appearance  of  irregularly- 
veined,  marble-like  projecting  dislocations,  with  intervening  fissures,  is  produced  by  immersing  the 
hot  glass  in  cold  water,  quickly  withdrawing  it,  reheating  the  ball  of  glass,  and  simultaneously  ex- 
panding it  by  blowing. 

Cameo  incrustation  is  also  of  modern  origin,  having  been  first  introduced  by  the  Bohemians  The 
figure  intended  for  incrustation  must  be  made  of  materials  requiring  a  higher  degree  of  heat  for 
their  fusion  than  the  glass  to  be  used.  The  figure,  having  been  heated,  is  introduced  into  a  cylindri- 
cal-shaped piece  of  glass,  attached  at  one  end  to  a  blow-pipe  and  open  at  the  other.  The  open  end 
is  then  closed,  leaving  the  figure  in  the  interior  of  the  hollow  pocket.  The  air  is  now  exhausted 
through  the  hollow  tube,  which  produces  a  collapse  and  causes  the  glass  and  figure  to  form  into  a 
homogeneous  mass.  In  making  "  paper  weights,"  thin  sections  of  little  ornamented  rods  are  placed 
in  a  circular  iron  mould  or  bed,  in  the  form  of  the  required  design.  A  workman  presses  a  piece  of 
hot  glass  on  the  end  of  a  punty  into  the  mould  and  takes  up  the  design.  Then  another  workman 
drops  a  piece  of  hot  glass  on  the  opposite  side  of  the  design.  The  whole  is  now  taken  to  the  fur- 
nace, where  the  parts  are  welded  into  a  hemispherical  form,  which  magnifies  the  interior  design  and 
presents  a  fine  picture  inclosed  within  the  transparent  setting. 

In  making  spun  glass,  the  workman  heats  one  end  of  a  tube  of  glass,  white  or  colored,  by  the 
flame  of  a  lamp,  and,  seizing  the  softened  end  with  a  pair  of  pincers,  draws  out  a  long  thread.  Ow- 
ing to  the  extreme  ductility  of  glass,  these  threads  can  be  drawn  to  an  extraordinary  fineness  and 
length.     In  some  eases  spun  glass  has  been  made  to  imitate  the  hair  of  animals. 

CracMe-glass  {verve  craqucle)  is  clear  glass  covered  with  an  opaque  layer  of  powdered  or  broken 
glass,  producing  a  rough  surface.  This  kind  of  glass  is  largely  made  in  Bohemia.  The  broken  glass 
is  spread  upon  an  iron  plate,  and  the  object  to  which  it  is  to  adhere  is,  while  yet  pasty,  rolled  upon 
the  fragments.     The  ordinary  blowing  process  follows. 


Aventurine  glass  is  a  very  beautiful  imitation  of  the  quartz  of  that  name.  It  is  yellowish  in 
color,  and  through  it  are  interspersed  immense  numbers  of  brilliant  tetrahedric  crystals  of  copper, 
protoxide  of  copper,  or  the  silicate  of  that  oxide.  When  polished,  this  glass  is  often  set  in  precious 
metal  for  jewelry.  The  crystals  are  produced  in  the  glass  while  it  is  jet  liquid.  As  copper,  iron, 
and  tin  exist  among  the  numerous  elements  which  compose  glass,  it  is  piobable  that  this  crystalliza- 
tion is  attributable  to  the  reduction  of  the  copper  oxide  by  the  last-mentioned  metals. 

Chronic  aventurine  is  made  of  sand,  carbonate  of  soda,  lime-spar,  and  bichromate  <>f  potash.  It 
contains  from  6  to  7  per  cent,  of  oxide  of  chromium,  about  half  of  which  is  combined  with  the  glass, 
giving  it  a  beautiful  greenish  color,  and  the  remainder  exists  dispersed  throughout  the  material  iu 
the  form  of  brilliant  crystals.     This  glass  is  also  used  for  jewelry. 

Paste,  or  straS8,  which  is  used  to  imitate  diamonds,  and  which  constitutes  all  the  cheap  gems  known 
under  a  multiplicity  of  sensational  names  intended  to  delude  the  ignorant,  is  a  superior  quality  of 
lead-glass,  of  the  following  composition,  according  to  Dumas  :  silex,  88.2  ;  oxide  of  lead,  53  ;  potash, 
7.8;  alumina,  1  ;  borax  and  arsenic  acid,  traces;  total,  100.  These  are  about  the  same  ingredients 
as  enter  into  the  fabrication  of  crystal,  it  is  very  soft,  and  is  easily  cut  or  scratched  by  other  varie- 
ties of  glass.  Its  distinguishing  characteristic  is  remarkable  brilliancy.  To  convert  clear  paste  into 
imitations  of  gems  other  than  the  diamond,  metallic  oxides  are  added.  Thus  the  artificial  topaz  con- 
sists of  1,000  parts  white  Btrass,  40  parts  antimony  glass,  and  1  part  purple  of  Cassius;  ruby,  the 
same,  but  heated  longer  and  containing  a  little  more  gold  ;  emerald,  1,000  parts  white  strass,  B  oxide 
of  copper,  and  .2  part  oxide  of  chromium;  sapphire,  1,000  parts  Btrass  and  lf>  oxide  of  cobalt; 
amethyst,  1,000  parts  strass,  8  oxide  of  mangant  Be,  1  oxide  of  cobalt,  and  2  purple  of  Cassius. 

Glass  pearls  are  largely  manufactured  in  Venice,  under  the  name  of  rassades  or  rocaiUes,  in  the 
same  manner  as  already  described  for  beads.  Verj  beautiful  imitation  pearls  called  baroque*  are 
made  in  Paris,  of  exceedingly  thin  glass  lined  with  gelatine  and  a  nacreous  matter  obtained  from 

Glass  Mosaics. — To  make  mosaic  pictures  in  glass,  small  cubes  of  enamel  are  used.  In  the  Vatican 
factories  in  Koine  this  material  is  produced  in  upward  ol  26,000  different  shades.  The  work  is 
begun  by  the  designer,  who  traces  on  pasteboard  in  colors  the  design  to  be  reproduced.  The  mosaic- 
setter  then  tills  a  shallow  tray  of  lead,  of  the  same  size  as  the  cartoon,  with  plaster,  and  draw-  the 
design  in  outline  on  the  BUrface  of  the  latter.  The  plaster  i-  then  gradually  removed  bit  by  bit,  and 
the  pieces  of  enamel  which  match  the  colors  on  the  design  are  inserted  in  its  place, the  hollows  being 
previously  covered  with  moistened  sand  of  a  greasy  nature  produced  from  a  voleanie  earth  found  on 
Vesuvius.  Where  the  cubes  of  enamel  have  to  turn  corners,  they  are  ground  to  fit  on  a  steel  disk 
supplied  with  emery  and  water.  When  the  cubes  are  all  set  in  place,  a  sheet  of  paper  or  cloth  is 
pasted  over  their  Surface,  care   being  taken   that   all   are   caused    to   adhere.      The  lead  tray  is  then 

reversed,  the  earth  backing  removed,  ami  a  mortar  composed  of  Roman  cement,  lime,  and  pozzuolana 

is  applied.  When  this  sets,  the  enamel  cubes  are  solidly  fixed,  and  it  only  remains  to  wash  off  the 
paper  or  remove  the  cloth,  and  insert  the  mosaic  in  its  frame  or  in  the  wall  which  it  is  to  decorate. 

Cutting  and  Wngraving  of  Glass. — Four  kinds  of  grinding-whocls  arc  used  in  glass-cutting:  l,a 
wheel  of  wrought  or  soft  cast-iron ;  2,  a  wheel  of  sandstone ;  3,  a  wooden  wheel ;  and  4,  a  cork 
wheel.  In  France,  where  this  operation  is  carried  to  the  greatest  degree  of  perfection,  a  so-called 
"company  of  cuttere"  includes  three  workmen,  namely,  the  ebauehcur,  tailleur,  and  polisseur,  or 
designer,  cutter,  and  polisher.  The  designer  is  usually  the  chief  of  the  company.  He  prepares  the 
design,  and  roughs  it  out  on  the  object  by  means  of  the  iron  wheel,  which  is  rotated  either  by  a  foot- 
treadle  or  by  a  motor.  The  wheel  is  mounted  vertically,  and  is  surmounted  by  a  conical  hopper 
filled  with  sand  and  water  nearly  in  the  state  of  mud.  This  falls  upon  the  wheel,  and  is  entrained 
by  its  rotation.  The  designer  applies  the  object  to  the  wheel,  so  that  the  friction  of  the  sand  grinds 
away  the  surface  at  the  desired  points.  The  object  now  passes  to  the  cutter,  who  in  his  turn  pre- 
sents the  piece  to  the  sandstone  wheel,  which  smooths  away  the  asperities  left  by  the  sand.  Finally 
the  object  goes  to  the  polisher,  who  finishes  its  surface  by  application  of  the  wooden  wheel  and 
pumice  powder,  and  lastly  of  the  cork  wheel  and  colcothar. 

The  wheels  employed  by  the  cutters  are  quite  large,  often  measuring  20  inches  in  diameter  and 
over.  Those  used  by  engravers,  on  the  contrary,  are  small,  rarely  exceeding  an  inch  or  two,  and 
decreasing  down  to  minute  disks  scarcely  larger  than  the  head  of  a  pin.  These  wheels  are  of  steel, 
copper,  sandstone,  ami  an  alloy  of  lead  and  tin.  Emery  powder  is  used  in  a  very  fine  state,  and  the 
lathe  is  operated  by  the  foot  of  the  workman.  This  mode  of  engraving  has  been  largely  supplanted, 
especially  for  coarse  work,  by  the  use  of  the  sand-blast.     (See  Sand-Blast.) 

Stained  Glass. — Glass-painting,  which  is  more  properly  a  process  of  staining,  differs  from  all  other 
styles  of  pictorial  art,  except  the  painting  of  porcelain.  The  colors  are  different,  being  wholly  of 
mineral  composition,  and  are  not  merely  laid  on  the  outside,  but  fixed  by  being  fused  into  the  mate- 
rial, undergoing  in  the  operation  chemical  changes  that  develop  the  brilliancy  and  transparency 
of  which  the  compounds  are  susceptible.  The  colors  are  mixed  with  a  flux  of  much  easier  fusion 
than  the  glass,  and  with  some  vehicle,  as  boiled  oil  or  spirits  of  turpentine.  The  mixture  is  usually 
laid  on  with  a  brush  as  in  ordinary  painting ;  and  the  glass  being  then  exposed  to  heat,  the  flux 
melts  and  sinks  into  the  body.  None  of  the  clear  bright  colors  are  perceived  until  the  work  is  com- 
pleted, and  the  artist  consequently  labors  under  great  disadvantage  in  applying  the  materials  that 
are  to  produce  them.  lie  is  guided  either  by  lines  drawn  on  the  back  side,  which  show  through,  or 
by  a  cartoon  or  drawing  on  paper  placed  there.  In  the  early  use  of  stained  glass  for  windows,  es- 
pecially in  churches,  brilliant  colors  were  highly  esteemed,  and  great  success  was  attained  in  the 
methods  of  coloring.  A  bright-red  color  was  imparted  by  the  ancients  with  the  protoxide  of  copper. 
In  later  times  it  was  found  impracticable  to  succeed  with  this  on  account  of  the  tendency  of  the 
copper  to  pass  to  a  peroxide  and  produce  a  green  tinge ;  but  the  practice  has  been  again  introduced 
with  success  by  the  Tyne  Company  in  England,  at  Choisy  in  France,  and  in  other  places.     The  dis- 


covery  of  the  preparation  of  gold  and  tin,  called  purple  of  Cassius,  also  afforded  another  means  of 
producing  a  brilliant  red. 

The  process  of  producing  a  painted  glass  window  is  an  interesting  one.  The  artist  first  makes 
an  outline  on  a  small  scale  of  the  stonework  of  the  window,  within  which  he  sketches  the  design, 
indicating  the  colors  to  be  used  and  the  general  treatment  of  the  subject.  A  full-sized  drawing  or 
cartoon  is  next  made,  from  which  a  "  cutting  drawing  "  is  traced,  showing  the  lines  where  the  strips 
of  lead  are  to  so,  and  omitting  all  other  details.  On  this  latter  drawing,  on  which  the  colors  of  the 
design  are  indicated  by  outlines,  the  pieces  of  different-colored  glass  are  laid  and  cut  with  a  diamond, 
eaelfpiece  being  cut  out  of  that  particular  color  or  tint  required.  The  artist  now  arranges  the  pieces 
of  different  colors  in  their  proper  places  on  the  cartoon,  and  traces  the  outline  of  the  design  upon 
them.  On  being  heated  in  an  oven,  the  opaque  lines  vitrify  and  are  formed  indelibly  on  the  surface 
of  the  glass.  After  the  outlines  have  been  thus  "  burnt"  on,  the  glass  is  taken  again  to  the  painter, 
who  covers  the  cartoon  with  a  sheet  of  colorless  glass,  or  if  large  a  portion  of  it  at  a  time.  Thus 
having  the  cartoon  for  a  guide,  he  arranges  in  their  proper  places  on  the  sheet  of  colorless  glass  the 
pieces°on  which  the  outlines  have  been  traced,  and  secures  them  firmly  with  drops  of  melted  resin 
and  beeswax,  or  other  suitable  substance.  The  sheet  of  colorless  glass,  with  the  pieces  thus  ar- 
ranged adhering  to  it,  is  placed  upon  an  easel,  and  the  shadows  of  the  picture  are  put  on  with  the 
same  material  as  that  used  in  tracing  the  outlines.  The  shading,  however,  is  not  traced  from  the 
cartoon,  as  were  the  outlines,  but  is  done  by  the  skill  and  experience  of  the  painter.  When  the 
shading  is  completed,  and  the  tints  of  yellow,  if  any  are  required,  are  put  on,  the  pieces  of  glass  are 
detached  from  the  colorless  sheet  and  again  subjected  to  heat,  for  the  purpose  of  "  burning  in  "  the 
shadows.  If  more  work  by  the  painter  is  required,  the  process  is  repeated,  the  glass  being  thus 
subjected  to  heat  in  some  instances  six  or  seven  times.  The  work  of  the  painter  being  completed, 
the  finished  pieces  are  taken  by  the  "leader,"  who,  having  arranged  them  by  the  aid  of  the  "cutting 
drawing"  so  as  to  form  the  entire  design,  fastens  them  together  by  means  of  strips  of  grooved  lead 
skillfully  fitted  around  the  edges  of  the  several  pieces.  If  the  window  is  a  large  one,  asis  generally 
the  case,  it  is  divided  into  parts  of  convenient  size,  which  are  fitted  together  when  the  window  is  put 
in  its  place.  Bars  of  iron  are  also  sometimes  placed  across  the  window  at  the  line  of  junction  and 
at  other  convenient  intervals.  This  general  process  of  producing  mosaic  stained-glass  windows  has 
been  in  use  from  the  earliest  times,  though  it  may  have  been  modified  in  some  of  its  details ;  and 
until  some  other  method  of  imparting  colors  to  glass  without  detracting  from  its  transparency  and 
brilliancy  is  discovered,  the  opaque  lead  lines  in  the  design  must  be  accepted  as  a  necessity. 

Gilding  on.  Glass. — This  operation  is  performed  by  the  same  means  as  the  similar  operations  on 
pottery;  with  the  difference,  however,  that  as  vitreous  products  are  much  more  fusible  than  ceramic 
materials,  the  proportions  of  vehicles  to  be  added  to  the  gold  or  to  the  coloring  oxides  are  much 
greater.  , 

Anew  process  of  gilding  by  M.  Dodon  is  thus  given  by  the  Monileur  tie  la  Ceramique:  Gold, 
chemically  pure,  is  dissolved  in  aqua  regia  (1  part  nitric  and  3  parts  hydrochloric  acid).  The  solu- 
tion effected,  the  excess  of  acids  is  evaporated  on  a  water-bath  till  crystallization  of  the  chloride  of 
gold  takes  place  ;  it  is  then  taken  off  and  diluted  with  distilled  water  of  such  quantity  as  to  make  a 
solution  containing  1  gramme  of  gold  to  200  cubic  centimetres  of  liquid ;  a  solution  of  caustic  soda 
is  then  added  until  the  liquid  exhibits  an  alkaline  reaction.  The  solution  of  gold  is  now  ready  for 
reduction.  As  a  reducing  agent  an  alcoholic  solution  of  common  illuminating  gas  is  used,  prepared 
by  simply  attaching  a  rubber  tube  to  a  gas-jet  and  passing  the  current  of  gas  for  about  an  hour 
through  a  quart  or'alcohol.  This  liquid  (which  should  be  kept  in  a  closed  vessel)  is  added  in  quan- 
tities of  from  2  to  3  cubic  centimetres  to  200  cubic  centimetres  of  the  alkaline  solution  of  gold 
before  mentioned  ;  the  liquid  soon  begins  to  turn  to  a  dark-green  color,  and  at  length  produces  the 
metallic  laver  of  gold  of  known  reflecting  power.  As  an  improvement  on  the  process,  as  well  as  for 
convenience  in  executing  it,  there  mavbe  added  to  the  alcoholic  solution  of  gas  an  equal  quantity  of 
glycerine  (28°  to  30°  B.)  previously  diluted  with  its  own  volume  of  distilled  water.  If  the  gold  em- 
ployed is  an  alloy,  the  foreign  metals  must  in  all  cases  be  first  removed ;  and  especially  the  least 
traces  of  silver,  because  the  very  smallest  quantity  of  this  metal  totally  prevents  the  regular  and 
uniform  deposition  of  the  gold. 

Iridescent  Glass,  as  manufactured  under  the  patent  of  Mr.  Thomas  W.  Webb,  is  produced  as  fol- 
lows :  Chloride  of  tin  or  tin  salt  is  burned  in  a  furnace,  and  the  glass,  having  an  affinity  for  it  when 
hot,  receives  the  fumes,  and  so  at  once  an  iridescent  surface  is  produced.  To  give  greater  depth  to 
the  color  or  tints,  nitrate  of  barium  and  strontium  is  used  in  small  proportions.  Very  remarkable 
effects  of  iridescence  also  are  produced  in  glass  by  long  burial  in  the  earth,  as  is  evidenced  by  the 
collection  of  ancient  Phoenician  glass  exhumed  in  the  island  of  Cyprus  by  General  Di  Cesnola.  Long 
exposure  to  ammoniacal  vapors  gives  a  somewhat  similar  result. 

Electroplating  of  Glass.—  Professor  A.  W.  Wright  has  succeeded  in  depositing  most  beautiful  films 
of  gold,  silver,  platinum,  and  bismuth  on  thin  glass  by  electro-metallurgical  means.  For  a  descrip- 
tion of  this  process,  see  Electro-met allurgy. 

Various  applications  of  glass  will  be  found  under  the  following  headings  :  For  method  of  ruling 
glass  to  produce  diffraction-gratings,  see  Dividing  Machines  ;  for  its  electrical  uses,  see  Electrical 
Machines,  Static.     As  to  cutting  glass  panes,  see  Diamond. 

GLASS-WARE,  MANUFACTURE  OF.  The  tools  used  by  makers  of  glass-ware  are  few  and 
simple,  the  various  operations  depending  for  success  principally  upon  acquired  dexterity,  skill  and 
judgment.  The  implements  are  represented  in  Fig.  2183.  The  first  in  importance  is  the  pipe  or  blow- 
ing tube,  shown  at  1,  made  of  wroucrht-iron,  4  or  5  feet  long,  with  a  bore  from  a  quarter  of  an  inch 
to  an  inch  in  diameter,  a  little  larger  at  the  mouth  end  than  at  the  other.  It  is  a  long  hand,  partly 
covered  with  wood,  with  which,  the  end  being  heated  red-hot,  the  workman  reaches  into  the  pot  of 
melted  matter  and  gathers  up  the  quantity  he  requires,  and  which  afterward  holds  the  article  in  the 



manipulations  to  which  he  subjects  it ;  and  it  is  at  the  same  time  the  air-tube  through  which  the 
breath  is  forced  to  expand  the  vessel,  or  through  which  water  is  sometimes  blown  to  produce  the 
same  effect  by  the  steam  it  generates.  A  solid  rod  of  iron,  called  a  punty  or  pontil,  serves  to  receive 
the  article  upon  its  end  when  freed  from  the  pipe,  adhesion  being  secured  by  the  softness  of  the 
glass  or  by  a  little  red-hot  lump  already  attached  to  the  punty.  Spring  tongs  (5),  like  sugar-tongs, 
are  used  to  take  up  bits  of  melted  glass;  and  a  heavier  pair,  called  pucellas  (2),  furnished  with  broad 
but  blunt  blades,  serve  to  give  shape  to  the  articles  as  the  instrument  in  the  right  hand  of  the  work- 
man is  pressed  upon  their  surface,  while,  seated  upon  his  bench,  he  causes  with  his  left  hand  the 
rod  holding  the  article  to  roll  up  and  down  the  two  long  iron  arms  of  his  seat,  upon  which  it  is  laid 
horizontally  before  him.  At  the  same  time  the  vessel  is  also  shaped  from  the  interior  as  well,  and 
is  occasionally  applied  to  the  opening  of  the  furnace  to  soften  it  entirely,  or  only  in  some  part  to 
which  greater  distention  is  given  by  blowing.  The  pucellas  arc  sometimes  provided  with  blades  of 
wood,  as  at  4.  Another  important  instrument  is  a  pair  of  shears  (3),  with  which  a  skillful  workman 
will  cut  off  with  one  clip  the  top  of  a  wine-glass,  as  he  twirls  it  round  with  the  rod  to  which  it  is 
attached  held  in  the  left  hand.  The  edge,  softened  in  the  fire,  is  then  smoothed  and  polished.  Be- 
sides these,  a  wooden  utensil  called  a  battledore  (6)  is  employed,  with  which  the  glass  is  flattened  by 
beating  when  necessary  ;  compasses  and  calipers  and  a  measure  stick  are  at  hand  for  measuring  ;  and 
a  slender  rod  of  iron  forked  at  one  end  is  used  to  take  up  the  articles,  and  carry  them  when  shaped 
to  the  annealing-oven,  in  which  they  are  left  for  some  time  to  be  tempered.  The  marver  (Fr. 
marbrc,  marble)  is  a  smooth  polished  cast-iron  slab,  upon  the  surface  of  which  the  workman  rolls 
the  glass  at  the  end  of  his  tube  in  order  to  give  it  a  perfectly  circular  form. 

]Yine-Gktsses. — The  manufacture  of  goblets,  tumblers,  and  similar  articles  of  table-ware  may  be 
illustrated  by  describing  how  a  wine-gla>s  in  three  parts  is  made.     The  workman,  having  gathered 



<m  the  end  of  a  blow-pipe  the  requisite  amount  of  glass,  as  shown  at  1,  Fig.  2184,  rolls  it  on  the 
marver  and  expands  it  by  blowing  into  the  tube  until  it  assumes  the  form  shown  at  2,  and  afterward, 
being  flattened  at  the  end  with  the  battledore,  that  at  3.  A  lump  of  glass  is  now  attached  to  the 
flat  end  of  the  bowl  (4),  which  the  workman  with  the  pucellas,  while  rotating  the  pipe  on  the  long 
arms  of  the  chair  in  which  he  sits,  transforms  into  the  shape  shown  at  5.  A  globe  is  now  attached 
to  the  end  of  this  stem  (6),  which  is  afterward  opened  and  flattened  into  the  form  represented  at  7. 
A  punty  tipped  with  a  small  knob  of  hot  glass  is  next  stuck  to  the  foot  of  the  wine  glass,  winch  is 
severed  from  the  blow-pipe  at  the  dotted"  line  shown  at  8.  The  top  of  the  glass  is  then  trimmed 
with  shears  (9),  after  which  it  is  flashed  and  finished  as  at  10.  It  is  now  severed  from  the  end  of 
the  punty  by  a  sharp  blow,  and  carried  by  a  boy  to  the  annealing-oven  on  the  end  of  a  forked  rod. 

Pressed  Glass. — In  the  manufacture  of  articles  by  pressing,  a  hollow  mould  is  used  of  steel  or 
iron,  with  its  interior  surface  so  designed  as  to  give  the  object  the  required  shape  and  figuration. 
This  mould  may  be  in  one  piece  or  consist  of  several  parts,  which  are  opened  when  the  moulded 
glass  is  taken  out.  The  process  will  be  illustrated  by  describing  the  production  of  a  tumbler.  A 
lump  of  glass  is  gathered  from  the  pot  on  the  end  of  a  punty  by  the  "  gatherer,"  and  being  held 
over  the  open  mould,  a  sufficient  quantity  is  cut  off  with  a  pair  of  scissors  by  another  workman  and 
drops  into  the  mould.  This  is  now  pushed  under  a  hand-press,  Fig.  2185,  and  a  smooth  iron  plun- 
ger is  brought  down  into  the  mould  with  such  force  that  the  hot  glass  is  made  to  fill  the  entire  space 
between  the  inside  of  the  mould  and  the  plunder,  whose  size  and  shape  are  the  same  as  those  of  the 
interior  of  the  tumbler.  The  plunger  being  raised  up,  the  mould  is  taken  from  the  press  and  turned 
over,  when  the  tumbler  is  made  to  drop  out  bottom  side  up.  A  punty  with  a  piece  of  hot  glass  at 
one  end  is  now  attached  to  the  bottom  of  the  tumbler,  which  is  heated  at  another  furnace  and 
smoothed  by  being  skillfully  rubbed  with  a  wooden  tool  while  rotated  on  the  arms  of  the  workman's 
chair ;  after  which  it  is  taken  on  a  fork  to  the  annealing-oven.  By  this  process  articles  can  be  pro- 
duced with  a  rapidity  not  attainable  in  the  case  of  blown  glass,  and  therefore  with  less  cost ;  but  the 
latter  is  generally  preferred. 



The  construction  of  a  mould  for  large  objects,  such  as  decanters,  is  represented  in  Fig.  21 86,  and 
a  section  of  it  in  Fig.  2187.  The  bottom  e  and  the  sides  a  of  the  body  form  the  lower  and  larger 
part  of  the  mould,  and  are  held  together  by  screws ;  the  upper  smaller  part  consists  of  two  halves, 
meeting  in  the  line  sz,  which  open  after  the  fashion  of  a  pair  of  tongs  when  turned  upon  the  hinge 
d.  That  they  may  not  be  extended  more  than  is  necessary,  the  two  wings  are  impeded  by  the  plugs 
o  fixed  to  the  ring  I.     The  workman  introduces  the  glass  globe  g,  attached  to  the  pipe,  into  the  body 

of  the  mould,  the  neck  portion  being  thrown  open,  and  blows  with  great  force  into  the  globe,  as  soon 
as  the  neck  portion  has  been  closed  by  an  attendant,  and  fixed  by  the  screw  m  (the  female  screw 
belonging  to  which  projects  at  n).  The  glass  is  forced  by  the  pressure  against  the  sides  of  the 
mould,  and  extends  in  the  form  of  a  cap  at  q,  above  the  margin,  where  the  pipe  is  detached  in  the 
direction  of  x  x.  The  cylinder  h,  and  another  similar  one,  more  at  the  back,  are  intended  for  the 
insertion  of  wooden  handles.  Massive  pieces,  such  as  plates,  are  formed  by  pouring  melted  glass 
between  two  plates  of  metal  composing  the  mould,  and  the  excess  of  glass  is  squeezed  out  from  the 
crevices  by  applying  weights  to  the  mould. 

All  articles  of  flint-glass,  whether  blown,  moulded,  or  pressed,  require  annealing  previous  to  cutting 
or  grinding.  As  they  are  frequently  constructed  of  very  different  thickness,  two  kilns,  which  can  be 
heated  to  different  temperatures,  are  requisite ;  the  larger  and  thicker  pieces  require  that  the  kiln 
should  be  much  hotter  than  is  necessary  for  thinner  pieces.  These  kilns  are  long,  low  buildings, 
arched  over  on  the  top.  The  various  articles  are  all  placed  on  sheet-iron  trays.  These  trays  are  put 
into  the  kiln  through  the  opening  in  front,  and  are  all  connected  together  by  hooks,  by  which  means 
they  can  be  moved  by  a  chain,  worked  by  windlass  or  similar  machinery,  to  the  farther  end  of  the 
kiln,  and  are  thus  gradually  withdrawn  from  the  hottest  part,,  and,  having  arrived  at  the  farther 
extremity,  are  removed  at  a  temperature  little  above  that  of  the  atmosphere. 

Moulded  or  pressed  glass  never  exhibits  its  full  amount  of  lustre,  nor  even  the  degree  of  sharpness 
of  the  metallic  mould ;  the  glass,  which  is  never  limpid  in  its  liquid  state,  is  first  cooled  by  contact 
with  the  metallic  surface,  and  is  thus  prevented  from  penetrating  into  the  sharp  corners  of  the 
mould,  nor  does  it  even  accommodate  itself  perfectly  to  the  flat  sides.  For  this  reason,  the  surface 
of  moulded  glass  is  not  even,  but  always  more  or  less  curved,  and  the  edges  are  not  sharp  ;  but  the 
use  of  moulds  as  a  preparatory  step  to  grinding  is  of  great  advantage  to  the  grinder,  as  the  vessel 
acquires  a  perfectly  regular  form,  and,  although  in  a  crude  state,  presents  all  the  prominent  and 
receding  facets  to  be  perfected  at  the  lathe. 

Bottles. — In  choosing  ingredients  for  this  kind  of  glass,  economy  is  the  chief  object.  The  follow- 
ing examples  are  calculated  for  100  lbs.  of  sand  :  For  champagne  bottles,  according  to  Jahkel — 200 
lbs.  feldspar,  20  lbs.  lime,  15  lbs.  common  salt,  125  lbs.  iron  slag;  ordinary  green  bottle-glass — 72 
lbs.  lime,  278-280  lbs.  lixiviated  wood  ashes;  English  bottle-glass — 100  lbs.  lixiviated  ashes,  40-90 
lbs.  kelp,  30-40  lbs.  wood-ashes,  80-100  lbs.  clay,  100  lbs.  cullet.  As  soon  as  the  working-holes 
are  opened,  the  workman  attaches  as  much  melted  glass  to  the  end  of  a  blow-pipe  as  he  considers 
necessary  for  the  production  of  a  single  bottle.  By  dipping  the  previously  warmed  pipe  into  the 
pot,  a  little  glass  remains  attached ;  after  turning  this  in  the  air  before  the  hole  until  it  is  cooled, 
and  blowing  slightly  into  it  to  render  it  hollow,  a  fresh  layer  of  glass  may  be  attached  to  it  in  the 
pot ;  to  this  a  third  is  added  in  the  same  manner,  until  the  ball  at  the  end  of  the  pipe  has  accu- 
mulated to  a  sufficient  size.  That  this  ball  may  become  uniformly  tractable  in  the  subsequent  form- 
ing, it  is  held  by  the  workman  in  the  flame  of  the  furnace  through  the  working-hole ;  it  is  then 
brought  into  one  of  the  round  concavities  of  the  marver  (constructed  either  from  a  stone,  marble,  or 
cast-iron  plate),  where  the  ball  gradually  assumes  the  form  of  a  pear-shaped  vessel,  Fig.  2184.  It 
acquires  this  shape  by  the  constant  rotary  motion  given  by  the  workman  to  the  pipe,  while  the  cool- 
ing and  stiffening  of  the  mass  is  rendered  uniform  by  the  marver,  and  it  is  prevented  from  shrinking 
together  by  constantly  blowing  into  the  pipe  with  very  little  force.  The  mass  of  metal  (metal  is  the 
technical  term  applied  to  glass  during  working)  must  be  equably  distributed  round  the  axis  of  the 
pipe,  and  advanced  in  front  of  its  mouth,  being  connected  with  it  only  by  a  short  neck. 

Thus  far  advanced,  the  glass  has  again  become  cool,  and  it  is  rewarmed  by  insertion  into  the  work- 







ing-hole,  in  such  a  manner  that  the  front  part  receives  the  chief  portion  of  the  heat  and  becomes  the 
softer.  The  pear-shaped  vessel  is  now  lengthened  by  the  blower,  and  its  form  is  approached  to  that 
of  a  bottle  by  a  threefold  operation:  by  blowing  into  the  tube  with  greater  force,  by  swinging  back- 
ward and  forward  in  the  manner  of  a  pendulum,  and  by  a  simultaneous  constant  rotary  motion  of 
the  pipe  round  its  axis.  The  globular  form,  which  the  glass  tends  to  assume  under  the  influence  of 
the  blowing,  is  converted  into  a  long  thin  egg-shape  by  the  swinging  motion,  Fig.  '2189.  The  rota- 
tion round  the  axis  of  the  pipe  is  an  essential  part  of  every  operation  in  glass-blowing.  The  flow- 
ing mass  of  glass  creates  a  powerful  current  of  air  in  an  upward  direction,  and  the  lower  portion 
becomes  cooled  in  consequence  much  more  than  the  upper.  This  naturally  creates  an  inequality  in 
the  resistance  offered  to  the  blowing,  and  the  upper  portion  would  be  more  expanded  than  the  lower 
if  the  cooling  influence  were  not  allowed  to  act  upon  all  parts  of  the  surface  alike  by  the  revolving 
motion  of  the  pipe;  and  this  is  particularly  the  ease  when  the  pipe  has  to  be  held  in  a  horizontal 
position.  The  mould  a  (a  simple  cylindrical  hollow  block  of  wood  or  iron)  is  placed  at  the  side  of 
the  workman  who  is  blowing  the  pear-shaped  vessel;  into  this  he  inserts  the  vessel  as  soon  as  it  has 
acquired  the  proper  thickness,  in  the  manner  represented  at  Fig.  2190,  and  by  blowing  forcibly  into 
thetube,  he  presses  the  glass  firmly  against  the  >ides  of  the  mould,  while,  by  a  kind  of  jerking  mo- 
tion, the  neck  IS  drawn  out  to  the  proper  length.  The  unfinished  bottle  is  again  warmed  in  the 
working-hole  in  such  a  manner  that  the  lower  part  only  is  heated,  while  the  oilier  parts  remain  com- 
paratively cool.  In  the  mean  time,  another  workman  or  a  boy  ha-  attached  a  sm;ill  quantity  of  glass 
to  another  pipe  or  rod  of  iron,  called  the  .punty,  which  is  also  kept  hot  in  the  working-hole.  Both 
workmen  now  -tand  opposite  to  each  other;  and  while  the  pipes  are  kept  constantly  turning,  the 
punty  is  forcibly  pressed  against  the  middle  of  the  lower  part  of  the  bottle,  which  is  thus  forced 
inward,  and  an  even  edge  is  produced,  upon  which  the  bottle  may  Btand  steadily.     The  bottle  remains 

for  some  moments  between  the  two  instru- 
ments, Fig.  2191,  until,  by  the  application 
of  cold  iron  or  a  drop  of  water,  the  neck 
can  be  separated  from  the  pipe.  This  sepa- 
ration is  an  operation  of  constant  recurrence 
in  the  glass-house,  anil  is  effected  by  a  sud- 
den change  of  temperature  produced  at  the 
point  of  separation  iu  the  hardened  glass, 
either  by  the  cold  application  of  a  drop  of 
water,  or  by  the  powerful  heat  of  a  red-hot 
iron  or  thread  oi  liquid  glass  from  the  pot. 
The  point  of  separation  must  often  be  re- 
heated in  order  to  fly  on  the  application  of 
cold  water.  The  bottle  i.-  now  supported  by 
the  punty,  as  Bhown  at  a,  Fig.  2191,  so  that 
the  neck  can  be  warmed,  and  the  sharp  c'ges 

melted  round  without  Boftcning  the  other 
parts.  A  rotating  motion  is  now  given  to 
the  red-hot  neck,  tin-  pipe  being  rolled  back- 
ward and  forward  upon  the  knees  of  the 
workman.  The  rim  for  strengthening  the 
neck  is  formed  from  a  drop  of  glass  taken 
from  the  pot  by  the  edge  of  the  flask  and 
wrapped  round  the  mouth  in  the  form  of  a 
thick  thread.  The  bottle,  which  is  now  fin- 
ished, Fig.  2192,  is  immediately  carried  by  the  punty-rod  to  the  annealing-oven  by  a  boy,  pushed  into 
its  proper  place,  and  the  punty-rod  is  lastly  detached  from  the  bottom  of  the  bottle  by  a  sudden  sharp 
jerk.  The  place  where  the  punty  was  attached  is  perceptible  in  every  bottle  blown  in  this  manner 
by  the  sharp  edges  where  the  fracture  occurred. 

Large  round  bottles  are  blown  without  the  use  of  a  mould;  and  when  of  very  large  size,  like  the 
carboys  for  sulphuric  acid,  the  aid  of  steam  is  called  in,  by  spurting  a  mouthful  of  water  into  the 
interior,  and  holding  the  mouth  of  the  pipe  with  the  thumb. 

Moulds  are  used  of  such  construction  as  to  secure  the  formation  of  a  bottle,  perfect  both  as 
TCgardsform  and  capacity,  at  one  single  operation,  without  reliance  upon  the  workman's  correctm  SS 
of  sight.  The  use  of  moulds  of  this  description,  like  that  of  Rickets,  which  is  easily  managed, 
affords  a  great  saving  of  time,  and  renders  the  repeated  heating  of  the  bottles  unnecessary. 

The  mould  consists  of  a  body  which  forms  the  belly  of  the  bottle  and  of  four  other  parts,  a  fixed 
bottom-piece  with  a  movable  piston  for  forming  the  concavity,  and  two  movable  pieces  for  the  neck. 
Two  treadles  set  these  different  parts  in  motion.  As  soon  as  the  workman  has  introduced  the 
hollow  lengthened  globe  into  the  belly  of  the  mould,  by  pressing  with  his  foot  upon  the  first  treadle, 
he  brings  up  the  neck-piece,  then  forces  the  glass  into  contact  with  all  parts  of  the  mould  by  a  ]  ow- 
erful  blast,  and  finishes  the  bottle  by  working  the  second  treadle,  which  forces  the  pestle  against  the 
bottom.     On  the  removal  of  the  pipe,  the  rim  of  the  neck  is  all  that  remains  to  be  perfected. 

Champagne  bottles  require  to  be  made  more  than  usually  strong  in  consequence  of  the  pressure 
exerted  by  the  carbonic  acid  inclosed  within  them,  and  they  are  particularly  liable  to  fracture  during 
the  bottle-fermentation  of  the  wine.  Yet  they  will  often  withstand  a  pressure  of  40  atmospheres 
and  upward  (=  600  lbs.  on  the  square  inch). 

The  Manufacture  of  Mirrors. — Plate-glass  has  to  undergo  three  operations  before  it  is  silvered. 
The  first  is  smoothing.  The  rough  plates  are  fastened  with  plaster  upon  a  stone  or  cast-iron  table. 
By  means  of  a  long  beam  of  iron  suspended  from  the  ceiling  and  moved  circularly,  masses  of  wood 




attached  to  said  beam  and  faced  with  cast-iron  are  rubbed  over  the  glass.  On  the  surface  of  the 
latter  coarse  quartz  sand  is  thrown  and  a  constant  fine  stream  of  water  is  supplied.  The  coarse 
sand  is  subsequently  replaced  by  a  finer  material,  and  this  last  by  coarse  emery.  As  soon  as  one 
side  of  the  glass  is  finished,  the  plate  is  turned  over  and  the  other  side  similarly  treated.  Another 
method,  largely  used  in  France  and  England,  consists  in  attaching  the  plates  to  a  circular  table  of 
15  or  18  feet  diameter,  which  is  rotated  about  a  central  pivot.  Above  the  glass  are  placed  heavy 
plates  of  wood  faced  with  cast-iron.  These  plates,  which  are  rotated  by  motion  imparted  from  the 
table,  but  in  an  opposite  direction,  have  counterweights,  so  that  their  pressure  upon  the  glass  may 
be  adjusted ;  by  means  of  this  double  movement  the  operation  is  greatly  expedited.  Sand  and  emery 
are  interposed  as  already  described. 

The  second  process  is  rubbing  with  fine  emery,  made  into  a  paste  with  water,  in  order  to  remove 
fine  scratches.  The  glass  rests  on  a  table,  and  upon  a  wet  cloth  to  prevent  its  sliding.  Another 
plate  of  glass  is  deposited  above  it,  and  the  two  surfaces  are  thus  rubbed  together  by  suitable 

The  third  process  is  polishing,  and  this  is  done  by  means  of  colcothar  or  red  peroxide  of  iron,  in 
a  pure  and  fine  state.     The  polishing  apparatus  is  represented  in  Fig.  2193.     The  glass  is  fastened 


to  the  movable  tables  E,  which  reciprocate  in  a  direction  relatively  perpendicular  to  that  of  the 
brushes  H H',  which  reciprocate  above  and  rub  upon  the  glass.  The  brushes  are  moved  by  the 
geared  mechanism  shown.     About  10  hours  is  required  to  polish  about  50  superficial  feet  of  glass. 

The  method  of  coating  the  plates  is  as  follows  :  A  large  stone  table,  ground  perfectly  smooth,  is 
so  arranged  as  to  be  easily  canted  a  little  on  one  side  by  means  of  a  screw  set  beneath  it.  Around 
the  edges  of  the  table  is  a  groove,  in  which  mercury  may  flow  and  drop  from  one  corner  into  bowls. 
The  table  is  first  made  perfectly  horizontal,  and  then  tin-foil  is  carefully  laid  over  it,  covering  a 
greater  space  than  the  glass  to  be  coated.  A  strip  of  glass  is  placed  along  each  of  three  sides  of  the 
foil  to  prevent  the  mercury  from  flowing  off.  The  metal  is  then  poured  from  ladles  upon  the  foil 
till  it  is  nearly  a  quarter  of  an  inch  deep,  and  its  tendency  to  flow  is  checked  by  its  affinity  for  the 
tin-foil  and  the  mechanical  obstruction  of  the  slips  of  glass.  The  plate  of  glass,  cleaned  with  espe- 
cial eare,  is  dexterously  slid  on  from  the  open  side,  and  its  advancing  edge  is  kept  in  the  mercury, 
so  that  no  air  or  floating  oxide  of  the  metal  or  other  impurities  can  get  between  the  glass  and  the 
clean  surface  of  the  mercury.  When  exactly  in  its  place,  it  is  held  till  one  edge  of  the  table  has 
been  elevated  10°  or  12°  and  the  superfluous  mercury  has  run  off.  Heavy  weights  are  placed  on  the 
glass,  and  it  is  left  for  several  hours.  It  is  then  turned  over  and  placed  upon  a  frame,  the  side 
covered  with  the  amalgam,  which  adheres  to  it,  being  uppermost.  In  this  position  the  amalgam 
becomes  hard,  and  the  plate  can  then  be  set  on  edge ;  but  for  several  weeks  it  is  necessary  to  guard 
against  turning  it  over,  as  until  the  amalgam  is  thoroughly  dried  the  coating  is  easily  injured. 

Several  serious  difficulties  attend  this  process.  The  health  of  the  workmen  is  so  affected  by  the 
fumes  of  the  mercury  that  they  can  rarely  follow  the  business  more  than  a  few  years ;  for  this  no 
remedy  has  been  found  so  effectual  as  thorough  ventilation  and  the  frequent  use  of  sulphur  baths. 
The  glass  plates  are  liable  to  be  broken  by  the  weights  placed  upon  them ;  and  the  coating  of  amal- 
gam is  frequently  spoiled  by  the  drops  of  mercury  removing  portions  of  it  as  they  trickle  down,  or 
by  its  crystallizing,  or  by  mechanical  abrasion.  Many  methods  of  silvering  have  been  contrived  and 
patented  with  the  view  of  obviating  these  defects,  some  of  which  are  important.  In  1855  a  patent 
was  granted  in  England  to  Tony  Petitjean  for  a  method  of  precipitating  silver,  gold,  or  platinum 
upon  glass,  so  as  to  form  a  coating  upon  it,  by  the  use  of  two  solutions,  the  effect  of  which  when 
mixed  upon  the  glass  is  to  decompose  each  other.  The  solutions  he  employed  were  different  com- 
pounds of  ammonio-nitrate  of  silver,  tartaric  acid,  and  distilled  water ;  and  they  were  placed  upon 
the  plate  while  this  was  at  the  temperature  of  150°  F.  The  precipitated  silver  within  20  minutes 
covered  the  glass,  to  which  it  adhered ;  and  the  solution  being  then  turned  off,  all  that  remained  to 
complete  the  mirror  was  to  wash  the  surface,  and  when  dry  cover  it  with  a  coat  of  varnish  to  protect 
it  from  injury.     The  silvering  thus  obtained  is  not  so  white,  and  is  rarely  so  free  from  blemishes,  as 

58  GLUE. 

the  amalgam  coating.  Iii  18-19  Mr.  Drayton  made  known  a  similar  method,  an  improvement  upon 
a  process  which  he  patented  in  1843.  He  employed  ammonia  1  oz.,  nitrate  of  silver  2  oz.,  water  3 
oz.,  and  alcohol  3  oz. ;  these,  being  carefully  mixed,  were  all  allowed  to  stand  a  lew  hours,  when  to 
each  ounce  of  the  liquid  was  added  an  ounce  of  saccharine  matter,  as  of  grape-sugar,  dissolved  in 
equal  portions  of  spirit  and  water.  Liebig  invented  a  method  of  coatiDg  glass  with  silver,  in  which, 
after  the  silver  coating  is  laid  on,  it  is  covered  with  a  coating  of  copper  precipitated  upon  it  by  the 
galvanic  current,  or  is  protected  by  varnish.  Silver  mirrors  are  now  extensively  made  in  New  York. 
For  platinizing  glass,  R.  Bottger  recommends  the  following  process:  Pour  rosemary  oil  upon  the  dry 
chloride  of  platinum  in  a  porcelain  dish,  and  knead  it  well  until  all  parts  are  moistened ;  then  rub 
this  up  with  five  times  its  weight  of  lavender  oil,  and  leave  the  liquid  a  short  time  to  clarify.  The 
objects  to  be  platinized  are  to  be  thinly  coated  with  the  preparation,  and  afterward  heated  for  a 
few  minutes  in  a  muHle  or  over  a  Bunsen  burner.  The  brilliancy  of  aluminum  has  caused  the  sug- 
gestion of  its  application  to  the  coating  of  mirrors;  but  no  successful  experiments  have  yet  been 
made  with  it  for  this  purpose. 

Large  mirrors  are  made  in  the  United  States  by  coating  the  imported  plates.  The  old  amalgama- 
tion method  with  tin-foil  and  mercury  is  preferred  to  any  of  the  more  recent  inventions,  by  reason 
of  the  greater  whiteness  and  brilliancy  of  the  reflection  and  the  greater  permanence  of  the  coating. 

GLUE.  All  animal  tissues  contain  an  adhesive  Bubstance  which  anatomists  call  histose,  in  accord- 
ance with  the  name  histology  given  to  the  study  of  the  formation  of  these  tissues.  When  they  are 
boiled  in  water,  the  histose  is  changed  into  a  new  substance,  called  gelatine,  dissolved  in  the  water, 
from  which  it  may  lie  separated  by  simple  evaporation,  when  it  forms  a  dry,  hard  substance,  which 
has  different  names  corresponding  with  the  various  sources  of  its  origin.  That  obtained  from  carti- 
lage is  called  chondrine  ;  from  bones,  hoofs,  and  hides,  glue  :  from  the  air-bladder  and  intestines  of 
fishes,  isinglass  ;  and  from  the  less  tenacious  and  adhesive  constituents  of  parchment  scraps  and 
some  other  animal  membranes,  size. 

The  best  kinds  of  ordinary  glue  are  made  from  fresh  bones,  cleared  of  fat  by  previous  boiling,  and 
also  offal  obtained  by  trimming  the  skins  for  tanners.  The  pieces  of  dried  skin  thus  obtained  are 
called  glue-pieces.  The  browner,  commoner  glue  i-  made  from  offal  from  Blaughter-houses,  cattle- 
hoof  s,  etc.  The  skin-pieces  arc  soaked  in  milk  of  lime  for  three  weeks,  the  lime  being  renewed 
every  week.  They  are  then  put  in  layers,  on  a  doping  pavement,  to  drain  and  dry,  and  tinned  over 
three  times  a  day.  They  are  afterward  soaked  in  weak  lime-water,  and  washed  in  baskets  under  a 
stream  of  water.  They  are  then  drained  and  exposed  to  the  air,  so  as  to  enable  the  adhering  lime 
to  absorb  carbonic  acid  from  the  atmosphere,  and  thus  lose  its  caustic  properties,  which  would  de- 
stroy part  of  the  glue  during  the  subsequent  boiling.  If  the  glue  is  to  be  used  as  gelatine  for  culi- 
nary purposes,  only  perfectly  cleaned,  fresh  bones  are  used.  Calf  bones  give  a  milky  glue;  those  of 
the  hog  produce  a  blackish  foam  which  mixes  in  the  solution;  while  the  product  from  those  of  the 
sheep  retains  always  the  peculiar  odor  of  the  fat  of  this  animal.  Beef-bones  are  preferred,  giving  a 
perfectly  transparent  glue,  sold  under  the  name  of  gelatine  or  isinglass.  The  materials  (bones, 
skins,  etc.)  are  placed  in  a  flat  copper  boiler,  upon  a  perforated  false  bottom,  placed  at  a  little  dis- 
tance over  the  bottom  of  the  boiler,  so  as  to  prevent  the  solid  material  from  touching  the  shell,  when 
it  would  stick  fast  and  be  burned.  The  boiler  is  filled  two-thirds  with  water,  ami  heat  is  applied. 
In  a  few  hours,  after  stirring  repeatedly,  the  liquid  is  drawn  off  in  successive  portions,  as  soon  as  it 
is  perceived  that  a  sample  taken  out  gelatinizes  in  cooling.  Experience  has  taught  that  too  long 
boiling  injures  the  glue.  The  test  for  this  cooled  gelatinized  material  is,  that  it  must  lie  fit  to  be 
cut  in  slices  with  a  wire.  Before  drawing  off  the  solution  the  fire  is  diminished,  so  as  to  stop  the 
boiling  and  allow  the  liquid  to  clarify  by  settling.  It  is  then  drawn  into  a  deep  boiler,  where  it 
settles  for  the  second  time,  remaining  hot  from  five  to  six  hours. 

The  principal  improvements  in  glue-making  devised  by  Mr.  Peter  Cooper  consist  in  the  use  of 
steam-heating  of  the  vessels,  and  the  application  of  heat  under  pressure,  by  which  more  glue  is  ex- 
tracted in  a  much  shorter  period  of  time  and  with  great  saving  of  fuel  ;  and  the  production  of  an 
opaque  porous  isinglass,  made  in  winter  only,  when  the  frost,  by  expanding  the  water  in  the  act  of 
freezing,  separates  the  glue  particles.  Being  subsequently  dried  in  the  frozen  state,  they  keep  their 
spongy  appearance,  making  them  much  more  easily  soluble,  and  thus  bettor  adapted  for  culinary 
purposes.  Another  improvement  is  the  addition  of  Paris  white  (tine  chalk)  to  the  glue  used  by 
cabinet-makers.  It  has  the  following  advantages:  1.  It  improves  the  adhesive  qualities.  2.  It 
makes  the  glue  look  more  white,  and  thus  gives  to  a  browner  glue  the  lighter  appearance  of  a  more 
expensive  quality.  3.  It  is  a  pecuniary  gain,  since  a  substance  costing  only  3  or  4  cents  per  pound 
is  added  to  one  costing  30  or  40  cents. 

Glue  is  also  made  from  leather  offal  and  old  leather,  by  means  of  the  action  of  15  per  cent,  of 
hydrated  lime  and  water  in  closed  vessels,  at  a  temperature  of  250"  P.,  and  consequently  two  atmo- 
spheres pressure.  In  this  way  the  leather  is  completely  decomposed.  Its  principal  constituents 
being  tannic  acid  combined  with  gelatine,  the  lime  takes  hold  of  the  tannic  acid,  forming  tannate  of 
lime,  while  the  gelatine  is  set  free  and  dissolves  in  the  water. 

The  strongest  glue  is  that  which  is  purest  and  which  gelatinizes  most  completely.  Good  glue, 
properly  prepared  and  well  applied,  will  unite  pieces  of  wood  with  a  degree  of  strength  winch  leaves 
nothing  to  be  desired.  The  fibres  of  the  hardest  and  toughest  wood  will  tear  asunder  before  the 
glued  surfaces  will  separate,  and  certainly  anything  more  than  this  would  be  unnecessary.  Mr. 
Bevan  found  that  when  two  cylinders  of  dry  ash,  each  an  inch  and  a  half  in  diameter,  were  glued 
together,  and  then  torn  asunder  after  a  lapse  of  24  hours,  it  required  a  force  of  1,260  lbs.  to  sep- 
arate them,  and  consequently  the  force  of  adhesion  was  equal  to  715  lbs.  per  square  inch.  From  a 
subsequent  experiment  on  solid  glue  he  found  that  its  cohesion  is  equal  to  4,000  lbs.  per  square  inch. 

The  precautions  necessary  in  applying  glue  are,  to  secure  perfect  contact  of  the  parts,  and  to  delay 
gelatinization  of  the  glue  until  the  joint  has  been  completed.     The  glue  should  therefore  be  used 


while  very  hot,  as  hot  as  it  will  bear,  and  in  very  cold  weather  the  wood  itself  should  be  warmed. 
The  glue  should  be  well  rubbed  in  with  a  stiff  brush,  and  the  two  surfaces  should  be  rubbed  well 
together  and  retained  in  contact  under  great  pressure  until  the  glue  has  become  somewhat  dry. 
Complete  dryness  rarely  takes  place  under  several  days ;  but  after  the  lapse  of  12  hours  the  joint 
becomes  tolerably  strong.  A  joint  made  in  this  way  is  probably  as  strong  as  can  be  made  by  any 
ordinary  process. 

Various  modes  of  keeping  glue  in  a  liquid  state  are  employed.  The  addition  of  a  little  nitric  acid 
(10  oz.  of  strong  acid  to  2  lbs.  of  dry  glue  dissolved  in  water)  will  prevent  the  glue  from  gelatinizing 
or  becoming  solid ;  and  the  further  addition  of  a  little  vinegar,  or  rather  of  pyroligneous  acid,  will 
prevent  it  from  moulding.  It  has  been  proposed  to  add  sulphate  or  chloride  of  zinc  to  common  glue 
for  the  purpose  of  keeping  it  liquid.  A  solution  of  shellac  in  alcohol  has  been  used  and  highly  ex- 
tolled as  a  substitute  for  common  glue.     It  forms  a  tolerable  liquid  cement,  but  is  far  inferior  to  glue. 

Marine  glue,  which  possesses  extraordinary  adhesive  properties,  is  a  preparation  of  caoutchouc 
dissolved  in  naphtha  or  oil  of  turpentine,  with  the  addition  of  shellac  after  the  solution  has  by  stand- 
ing several  days  acquired  the  consistence  of  cream.  Two  or  three  parts  by  weight  of  shellac  are 
used  for  one  of  the  solution. 

GOLD-BEATING.  The  art  of  preparing  what  is  well  known  under  the  name  of  gold  leaf,  in 
which  gold  is  hammered  or  beaten  into  plates,  whose  average  thickness  at  the  present  day  may  be 
taken  at  2  soWu  of  an  inch. 

To  manufacture  gold  leaf,  the  metal  is  required  in  theory  to  be  in  a  state  of  purity.  All  alloy  is  at 
the  expense  of  malleability.  But  in  practice  this  is  rarely  if  ever  attained,  and  the  usual  fineness  is 
that  of  coin,  which  in  France  and  the  United  States  is  90  per  cent. ;  in  Great  Britain,  91$  per  cent. ; 
and  in  Bavaria,  where  the  principal  amount  of  gold-beating  in  Germany  is  done,  97nj  per  cent.  fine. 
In  France  it  was  stated  about  1820  that  the  most  approved  practice  was  to  mix  equal  parts  of  old 
Spanish  coin  and  pure  gold,  which  would  result  in  an  average  proportion  of  95f  per  cent.  fine. 
Below  75  per  cent,  fine,  the  manufacture  would  be,  in  labor  and  waste,  a  losing  business. 

The  principal  aim  of  alloying,  when  it  is  done  of  design,  seems  to  be  the  production  of  a  variety 
0f  Color — silver  making  the  leaf  pale,  copper  deepening  the  tint.  These  effects  are  more  particularly 
noticed  in  the  article  Allots  ;  they  are  similar  in  the  leaf  as  in  the  more  solid  masses ;  only  in  the 
state  of  tenuity,  the  green  and  purple  tinge  is  more  easily  excited  and  more  vividly  displayed.  What- 
ever may  be  the  character  and  degree  of  alloy,  the  manipulations  of  the  gold-beater  are  the  same  in 
kind,  and  will  be  now  briefly  described. 

1.  Casting. — The  metal  is  placed,  with  a  little  borax  to  promote  fusion,  in  a  black-lead  crucible,  or 
crucibles,  and  set  in  a  furnace.  When  perfectly  melted,  it  is  poured  into  cast-iron  moulds,  3  or  4 
inches  long,  three-quarters  of  an  inch  wide,  and  about  half  an  inch  deep,  and  holding  each  about 
1,000  grains  of  metal.  These  moulds  are  made  with  faces  a  little  concave,  to  allow  the  cast  to  draw 
easily ;  and  before  pouring,  they  are  heated,  and  rubbed  with  linseed  oil  or  tallow  on  the  inside,  to 
drive  off  moisture  and  promote  an  easy  separation.  When  sufficiently  cool,  the  ingot  is  taken  out, 
and  reheated  in  an  open  fire,  or  a  small  annealing-furnace,  by  which  it  is  softened,  and  the  adhering 
grease  driven  off. 

2.  Laminating. — In  older  times  this  was  effected  entirely  by  the  hand-hammer ;  now  a  flatting- 
mill  or  laminating  rolls  are  employed.  The  French  still  use,  however,  a  preliminary  forging  upon  a 
steel  anvil  (of  3-inch  by  4-inch  sides),  with  a  hammer  of  about  3  lbs.  weight.  The  face  of  this 
hammer  is  about  U  inch  square,  and  its  handle  about  6i  inches.  With  this  they  bring  down  the 
thickness  of  the  ingot  to  one-sixth  or  one-seventh  of  an  inch.  The  English  perform  the  whole  of  the 
operation  in  the  rolls.  As  the  success  of  the  work  and  the  excellence  of  the  leaf  ultimately  depend 
a  good  deal  upon  the  uniformity  of  the  lamination,  care  is  taken  to  use  a  proper  and  accurate  ma- 
chine. These  machines  have  been  successively  improved,  until  now  there  is  little  if  anything  left  to 
be  desired.  During  the  hardening  processes  of  lamination  and  forging,  if  the  latter  be  employed, 
the  ribbon  has  to  be  frequently  annealed,  to  prevent  cracking.  Formerly  the  lamination  was  thought 
sufficient  which  had  brought  the  thickness  down  to  one-twenty-fifth  of  an  inch,  with  a  width  of  one 
inch ;  and  the  balance  was  done  by  hand,  cutting  the  ribbon  into  lengths  of  U  inch,  piling  24  of  the 
lengths  evenly  together,  and  forging  them  all  at  once  till  they  came  square.  This  is  the  practice 
with  some  of  the  French  and  German  gold-beaters  to  this  day ;  but  others,  haying  access  to  more 
perfect  machinery,  continue  its  application  to  the  lamination  until  the  thickness  is  brought  to  about 
7-feo  of  an  inch.  As  dimensions  like  this  cease  to  be  appreciable,  the  degree  of  lamination  is  esti- 
mated by  weight ;  and  the  direction  usually  is,  to  bring  it  down  until  a  square  inch  of  ribbon  weighs 
6£  grains.     In  this  state  it  is  ready  for  the  beating  proper. 

"3.  Beating.— The  implements  and  fixtures  for  this  are,  an  anvil,  hammers,  skins,  shears,  parting- 
knives,  etc.  The  anvil  is  a  block  of  marble,  weighing  250  or  300  lbs.  or  more,  at  pleasure,  with  a 
face  of  9  inches  to  1  foot  square,  carefully  made  even  and  smooth.  This  is  set  in  a  frame  of  wood- 
work, strong  and  solid,  and  upon  a  firm  foundation.  A  ledge,  5  or  6  inches  high,  runs  round  three 
sides  of  the  frame  ;  to  the  remaining  side  an  apron  of  leather  is  attached,  which  is  lifted  by  the 
workman.  The  object  of  all  this  is  to  catch  and  retain  fragments  of  the  precious  metal.  The 
hammers  are,  ordinarily,  four  in  number,  varying  in  weight.  Their  faces  are  from  3  to  5  inches  in 
diameter,  and  slightly  convex.  The  weight  of  the  first  or  flat  hammer  is  about  15  lbs. ;  the  second 
(which  the  French  term  the  commencing  hammer)  weighs  from  6  to  8  lbs. ;  the  third,  or  spreading 
hammer,  with  a  smaller  face,  and  more  convex,  weighs  about  5  lbs.  only ;  and  the  last,  or  finishing 
hammer,  is  again  a  heavy  one  of  10  or  12  lbs.,  with  quite  a  convex  face.  The  skins  are  of  parch- 
ment and  vellum  and  the  intestine  already  spoken  of,  cut,  the  two  former  into  squares  of  about  4 
inches,  and  the  last  of  5  inches.  Besides  these,  there  are  packing-boxes,  also  of  parchment,  made 
on  a  form,  and  cemented  together,  open  at  two  opposite  ends,  and  in  pairs,  so  that  one  will  slip  into 
the  other,  by  which  the  open  ends  are  closed.     The  knives  are  pieces  of  cane,  set  into  a  frame,  both 


four-square  and  cruciform,  with  sharpened  edges  that  divide  the  attenuated  leaf  better  than  any 
other  implement,  by  pressure  downward  only.  When  the  leaf  becomes  very  thin,  any  other  motion 
would  drag  it. 

Provided  with  these  and  other  tools  that  do  not  require  special  mention,  the  workman  lays  off  the 
ribbon,  which  comes  from  the  laminating  as  nearly  as  possible  one  inch  in  width,  into  lengths  also 
of  one  inch.  This  he  does  with  dividers  or  a  scale,  and  cuts  off  afterward  with  shears.  This  is  on 
the  supposition  that  the  rolliug  has  been  uniform,  and  equal  surfaces  therefore  should  give  equal 
weights.  He  then  arranges  these  squares  into  piles  of  generally  150  pieces,  laying  each  leaf  on  a 
piece  of  the  vellum  before  spoken  of,  as  near  as  may  be  in  the  centre,  with  their  edges  even.  About 
twenty  extra  vellums  are  placed  on  top  and  at  bottom,  and  the  pack  is  then  of  proper  size  to  be 
pushed  smoothly  into  one  of  the  parchment  envelopes,  which  is  then  in  its  turn  pushed  into  its  mate, 
and  the  whole  thus  inclosed  on  all  four  sides.  The  pack  is  then  laid  on  the  nun  hie  anvil,  and  beaten 
until  the  small  gold  leaf  is  extended  to  the  size  of  the  vellum.  It  is  in  the  judicious  uniformity  of 
direction  and  force  of  the  blows  that  the  skill  of  the  workman  is  displayed.  Great  dexterity  is,  in 
fact,  attained  ;  the  hammer  is  shifted  from  hand  to  hand  for  relief  without  interfering  with  the 
regularity  of  the  stroke ;  and  when  it  is  recollected  that  the  absolute  effect  of  the  average  hammer 
with  the  average  blow  is  equivalent  to  the  steady  pressure  of  about  2, WOO  lbs.  on  the  square  inch, 
there  will  be  seen  to  be  need  for  discretion  in  the  application  of  such  a  force. 

During  the  beating,  the  pack  is  frequently  turned,  so  as  to  beat  on  the  bottom  as  well  as  the  top 
(as  a  skillful  workman  will  do  without  losing  the  stroke),  and  also  folded  or  rolled  in  the  hand,  to 
secure  a  proper  detachment  of  the  surfaces.  It  is  also  opened  from  time  to  time  to  watch  the  effect, 
and  shift  the  leaves  from  the  centre  to  the  outsides,  that  the  pressure  may  be  uniform.  When  the 
gold  has  been  extended  to  the  size  of  the  vellums,  about  sixteen  times  its  original  dimensions,  it  is 
taken  out,  cut  up  into  four  squares,  repacked  as  before,  only  with  gold-beaters'  skin  instead  of 
vellum,  and  beaten  over  until  similarly  extended  again.  The  caution  of  folding  the  pack  to  loosen 
the  leaves  is  even  more  necessary  now  than  before,  and  so  of  opening  and  shifting.  When  it  has 
attained  the  size  of  the  skins,  it  is  removed,  parted  into  squares  again,  but  this  time  with  the  cane, 
repacked,  and  rebeaten  as  before  into  leaves  of  3  to  3i  inches  square.  It  is  estimated  that  the 
aggregate  surface  of  the  leaves  is  now  192  times  larger  than  it  was  originally  ;  and  their  thickness 
may  be  taken  at  tteWtt  of  an  inch,  which  is  about  the  average  of  English  gold  leaf,  and  corresponds 
to  an  extension  of  about  100  square  feet  to  the  ounce.  But  the  operation  is  frequently  carried 
further  by  repeated  beatings,  till  an  ounce  is  extended  over  160  square  feet,  corresponding  to  a  cal- 
culated thickness  of  j^WiJ  oi  an  inch  aearly.  The  French  gold-beaters  claim — and  their  statement 
of  weight  worked  on  and  number  of  leaves  produced  warrants  the  claim — to  carry  it  down  ordinarily 
much  further  than  this ;  and  our  statement  at  the  beginning  of  zTTurnns  of  an  inch  is  probably  even 
within  the  average  result,  and  much  within  the  possible  limits,  of  malleability,  if  these  were,  without 
regard  to  expense  of  time  and  waste  of  metal,  the  only  points  to  be  reached. 

The  French  workmen  arc  also  very  precise  in  the  number  of  pieces,  both  of  leaf  and  of  bandruche 
and  vellum,  which  go  to  the  packs  in  each  of  the  five  several  steps  that  comprise  their  beating.  As 
the  fruit  of  experience,  no  doubt,  they  have  ascertained  the  number  which  best  suits  the  respective 
implements.  The  English  and  Germans  pack  in  different  numbers,  it  may  be  supposed  with  the 
same  reason;  but  the  principles  of  the  operation  are  in  all  the  same. 

When  the  leaf  is  considered  as  finished,  the  last  thing  is  to  put  it  in  the  square  books,  such  as  we 
see  in  commerce.  These  are  made  of  smooth  paper,  frequently  reddish-colored,  on  purpose  to 
heighten  the  lustre  of  the  gold,  and  well  rubbed  with  Armenian  bole  to  prevent  adhesion.  There 
are  two  sizes,  one  about  4£,  the  other  3f  inches  square.  The  pack,  withdrawn  from  its  parchment 
envelopes,  is  held  by  one  of  its  angles ;  and,  with  a  pair  of  wooden  pliers,  each  leaf  is  withdrawn, 
and  laid,  aided  by  the  breath,  upon  a  leathern  cushion,  where,  with  the  cane  knives,  it  is  parted  at 
once  or  successively  into  four  pieces,  the  size  of  the  book.  These  pieces  are  then  similarly  trans- 
ferred to  the  book,  each  between  separate  leaves.  The  book  holds,  very  uniformly,  25  leaves  of 
gold.  When  filled,  it  is  pressed  hard  with  a  piece  of  wood  of  its  own  size,  so  as  to  bring  its  edges 
close  ;  and  with  a  piece  of  linen  any  projecting  pieces  of  gold  leaf  are  readily  wiped  off.  Afterward 
the  books  are  put  up  in  packages  of  a  dozen  ordinarily,  for  sale.  The  French  artists  allow  between 
3  and  4  days  for  finishing  4  oz.  of  gold.  They  estimate  the  loss  in  trimmings,  waste  leaves,  etc.,  at 
50  per  cent.,  and  consider  the  remaining  2  oz.  (964.6  grains  English)  as  yielding  12,600  leaves  of 
the  smallest  size ;  but  there  is  no  authentic  experiment  of  weighings  and  measurings  in  this  respect. 

The  parchment  employed  is  used  as  it  comes  from  the  manufacturer,  only  cutting  out  of  the  sheets 
those  parts,  of  suitable  size,  which  are  softest  and  of  most  uniform  thickness.  The  vellum,  which  is 
produced  of  the  finest  and  softest,  is  not  further  treated  than  by  well  washing  it  in  cold  water,  dry- 
ing it  in  the  air  under  a  press,  and  then  powdering  it  with  finely  calcined  and  reduced  selenite. 
W'hether  the  implement  used  for  this  has  any  special  influence  will  not  be  affirmed  or  denied ;  but 
the  uniform  practice,  in  France  at  least,  is  to  use  a  hare's  foot. 

The  preparation  of  gold-beaters'  skin,  from  the  colon  of  the  ox,  has  been  already  spoken  of  as  a 
secret  maintained  by  the  few  who  furnish  the  article.  Whatever  their  processes  may  be,  the  gold- 
beater is  accustomed  to  test  and  treat  it  still  further  for  himself.  Thus,  he  first  sweats  it,  by  placing 
it  between  a  fold  of  foolscap  ;  making  a  pile  of  many  pieces,  he  treats  it  to  a  hearty  hammering 
until  it  ceases  to  give  out  any  grease  to  the  paper.  Next,  he  moistens  it  with  an  infusion  of  nutmeg, 
cinnamon,  or  other  spicy  aromatics,  with  the  view  of  preserving  it,  dries  it  in  the  air,  moistens  again 
as  often  as  he  sees  fit,  and  finally  dries  and  presses  it  for  use.  Since  the  introduction  of  creosote, 
this  (as  well  as  may  be  judged  from  the  odor  of  some  recent  skins)  has  been  applied,  and  no  doubt 
more  effectually.  After  the  skins  have  served  some  time  (some  TO  or  80  beatings,  for  instance), 
they  become  inspissated,  or  wiry,  or  both,  and  no  longer  allow  the  proper  extension  of  the  gold. 
This  may  be  cured  by  laying  them  a  half  day  between  leaves  of  paper  wetted  with  Rhenish  or 




Moselle  wine,  or  even  vinegar  and  water.  When  thoroughly  moistened,  they  are  placed  between 
layers  of  parchment,  enveloped,  and  beaten  until  dry.  This  beating  frequently  takes  a  whole  day. 
They  are  then  powdered  with  selenite,  and  fit  for  use.  While  yet  fresh,  the  skins  are  very  liable  to 
be  affected  by  moisture,  which  they  absorb  from  the  atmosphere.  They  must  be,  therefore,  always 
dried  before  using,  which  in  France  is  done  by  heat  in  a  screw-press.  Care  is  taken  not  to  desiccate 
too  much,  which  withers  and  causes  them  to  crack  under  the  hammer. 

The  methods  which  have  been  described  here  are  also  applicable  in  their  measure  to  silver,  copper, 
and  platinum. 

A  sort  of  gold  leaf,  called  party  gold  leaf,  is  sometimes  used,  made  with  a  combination  of  gold  and 
silver.  Separate  leaves  are  taken  of  these  metals,  the  silver  being  about  three  times  as  thick  as  the 
gold,  heated  and  laminated  together,  so  as  to  produce  an  alloy  or  welding  of  their  surfaces.  The 
resulting  party-colored  ribbon  is  then  beaten  as  if  it  were  all  of  gold.  Its  extensibility  is,  of  course, 
not  so  great.  *  There  is  another  false  gold  leaf,  which  is  better  known  as  Dutch  gold  leaf.  It  is,  in 
fact,  a  ribbon  of  brass,  wash-gilded,  sheared  into  leaves,  and  then  beaten  in  the  manner,  and  with 
more  or  less  of  the  precautions,  that  have  been  described.  When  new,  it  is  difficult  to  be  distin- 
guished from  true  gold  leaf;  but  it  is  soon  tarnished  by  the  air,  and  is  unfit  for  any  gilding  that  is 
not  to  be  varnished. 

GONIOMETER.  An  instrument  for  measuring  angles,  and  more  particularly  the  angles  formed 
by  the  faces  of  crystals.  The  instrument,  chiefly  used  by  mineralogists,  was  invented  by  Dr.  Wol- 
laston.  It  consists  of  a  brass  circle  graduated  on  the  edge,  and  furnished  with  a  vernier,  by  which 
the  divisions  may  be  read  correct  to  a  minute.  The  circle  moves  in  a  vertical  plane,  and  is  supported 
on  a  stand.  The  axis  of  the  circle  is  a  hollow  tube,  within  which  is  a  smaller  axis,  fitting  so  tightly 
that  when  turned  round  it  carries  the  other  axis,  and  consequently  the  wheel,  along  with  it,  unless 
the  latter  is  prevented  from  moving.  The  interior  axis  is  furnished  with  a  milled  head  A,  Fig.  2194, 
and  the  exterior  with  a  milled  head  B  ;  so  that  when  the  head  A  is  held  and  B  turned,  the  circle  may 
be  moved  independently  of  the  smaller  axis ;  and  when  B  is  held  and  A  turned, 
the  smaller  axis  may  be  turned  independently  of  the  circle.  Attached  to  the 
end  of  the  smaller  axis  is  a  sort  of  universal  joint,  capable  of  being  fixed  in 
different  positions  by  means  of  screws.  The  crystal  to  be  examined  is  attached 
to  the  joint  at  C  by  a  little  soft  wax,  and  placed  so  that  its  edge  shall  be  par- 
allel to  the  axis  of  motion ;  winch  adjustment  is  obtained  by  placing  it  so  that 
the  image  of  some  horizontal  object,  as  the  bar  of  a  window,  successively 
reflected  from  the  two  faces  of  the  crystal,  coincides  with  another  horizontal 
line  seen  by  direct  virion.  When  this  adjustment  has  been  made,  the  instru- 
ment is  turned  till  the  horizontal  object  is  seen  reflected  from  one  of  the 
faces.  The  smaller  axis  is  then  held  fast,  and  the  other  turned  till  the  index 
of  the  vernier  points  to  the  zero  of  the  graduated  limb.  The  circle  is  then 
turned  round,  along  with  the  smaller  axis,  till  the  same  object  is  seen  in  the 
same  position  by  reflection  from  the  other  face  of  the  crystal ;  when  the  arc 

passed  through  by  the  circle  is  obviously  the  supplement  of  the  angle  formed  by  the  two  faces  of  the 
crystal.  In  order,  however,  to  avoid  calculation,  the  supplements  of  the  angles  are  marked  on  the 
limb,  so  that  the  angle  to  be  measured  is  read  off  immediately. 

The  name  goniometer  is  also  applied  to  a  surveying  instrument,  somewhat  similar  to  a  theodolite. 

GOUGE.     See  Lathe-Tools,  Turning. 

GOVERNORS.  The  ordinary  steam-engine  governor  consists  of  two  heavy  balls  suspended  by 
links  from  a  spindle,  forming  a  combination  known  as  the  conical  pendulum,  and  caused  to  revolve 
by  some  connection  with  the  shaft  of  the  engine.  A  conical  pendulum,  if  there  is  no  friction  in  the 
joints  of  the  rods,  stands  in  a  position  corresponding  to  the  speed  at  which  it  is  running.  The 
height  of  the  pendulum  is  the  vertical  distance  of  the  vertex  of  the  cone  formed  by  the  links,  or  the 
links  produced,  above  the  plane  of  the  centres  of  the  balls ;  and  this  height,  which  determines  the  posi- 
tion of  the  balls,  is  equal  to  the  following  expression,  when  there  is  no  friction  in  the  joints,  or  other 

resistance :  -, ; — : — ; nr    If,  for  example,  the  number  of  revolutions  per  minute  is  100, 

(revolutions  per  niinute)  . 

the  height  is  35,208  -4-  10,000,  or  about  3i  inches.  The  following  table,  calculated  by  Mr.  Charles 
T.  Porter,  gives  the  speeds  corresponding  to  various  heights : 


Revolutions  per 


Revolutions  per 


Revolutions  per 


Revolutions  per 





























4s. 4 























•   16.5 













88 .4 













































The  actual  height  at  which  the  balls  revolve,  in  practice,  is  ordinarily  much  greater  than  that  given 
in  the  preceding  table — partly  for  the  reason  that  there  is  some  friction  in  the  joints,  but  principally 



because  a  weight  or  some  other  resistance  is  added,  to  increase  the  height.  The  advantage  of  this 
addition  can  readily  be  shown.  The  object  of  a  steam-engine  governor  is  to  act  on  the  throttle-valve 
or  cut-off  mechanism  in  such  a  manner,  that  when  the  load  of  the  engine  is  increased  more  steam 
will  be  furnished,  and  when  the  load  is  diminished  the  supply  of  steam  will  also  be  cut  off  to  a 
corresponding  extent.  By  reference  to  the  table,  it  will  be  seen  that  for  a  given  change  in  the  speed 
of  the  governor  the  change  in  the  position  of  the  balls  is  much  greater  as  the  height  of  the  pendulum 
increases;  so  the  effect  of  increasing  this  height  is  to  render  the  governor  more  sensitive.  There 
are  various  devices  for  increasing  the  height  corresponding  to  a  given  speed  ;  but  the  general  prin- 
ciple upon  which  they  act  is  essentially  the  same  as  in  Porter's  governor,  Fig.  219.%  which  is  prob- 
ably in  more  extensive  use  than  any  other  form.  It  will  be  seen  that  the  balls  of  the  governor  are 
comparatively  light,  and  that  they  are  connected  to  a  heavy  central  weight  by  levers  of  the  same 
length  as  those  connecting  them  to  the  spindle.     If  such  a  governor  is  revolving  freely,  the  height 

2  IF  +  B 
will  be  to  the  height  of  an  ordinary  pendulum  governor  as  1  is  to —  ;  in  which  expression  W 

is  the  central  weight,  and  B  the  weight  of  the  two  balls.  Thus,  if  the  weight  of  the  balls  is  10(1  lbs., 
and  the  central  weight  is  500  lbs.,  the  height  of  this  governor  at  any  given  speed  is  11  times  the 
height  of  an  ordinary  pendulum  governor.     Pickering's  governor,  Fig.  2196,  acts  on  the  same  general 

principle  as  Porter's,  but  the  position  of  the  balls  is  controlled  by  springs  of  a  peculiar  form,  instead 
of  by  weights.  These  two  governors  may  be  considered  as  representative  of  the  best  modern  prac- 
tice in  regard  to  pendulum  governors,  although  there  are  various  modifications  introduced  by  other 
makers,  of  more  or  less  value. 

The  governors  that  have  been  described  are  position  governors ;  that  is,  they  regulate  an  engine 
by  continually  changing  from  one  position  to  another,  alternately  increasing  the  "speed  of  the  engine 
and  diminishing  it,  within  a  given  range.  In  the  case  of  governors  similar  to  Porter's  and  Picker- 
ing's, the  action  is  very  similar  to  that  of  isochronous  governors,  which  have  the  same  height  for  all 
speeds,  and  so  can  remain  without  action  on  the  controlling  mechanism  at  one  speed  only."  Isochro- 
nous pendulum  governors  are  commonly  made  with  rods  having  flexible  ends  hung  to  curved  guides 
in  the  form  of  evolutes  of  a  parabola,  so  that  as  the  balls  rise  they  describe  parabolic  arcs.  The 
balls  themselves  are  sometimes  guided  by  parabolic  arcs  as  they  rise.  The  manner  of  designing  such 
governors  is  explained  in  the  Scientific  American  for  Dec.  26,  1874. 

The  Huntoon  governor,  practically  isochronous  in  its  action,  and  representative  of  another  class  of 
governors,  is  represented  in  Figs.  2197  to  2199,  and  is  thus  described  by  a  writer  in  the  Polytechnic 
Eeview  for  Sept.  16,  1876: 

_  "The  corrugated  cylinder  A,  Figs.  2198  and  2199,  is  filled  to  about  two-thirds  of  its  capacity  with 
oil.  On  the  inside,  at  the  ends  and  on  the  periphery,  are  eight  ribs,  and  between  them  intermediate 
ones  on  the  periphery  only.  Inside  of  the  cylinder  is  the  paddle-wheel  B,  having  six  blades,  and 
which,  as  shown  in  Fig.  2199,  has  but  slight  clearance  in  passing  the  ribs.  The  shaft  or  spindle  of 
the  paddle-wheel  passes  through  a  stuffing-box  and  a  journal-bearing  in  the  housing  or  frame,  and 
carries  the  flanged  pulley  shown  in  Fig.  2197.  Into  the  other  head  of  the  cylinder  is  screwed  a  stud 
which  forms  the  journal  for  that  end,  and  carries  the  pinion  I),  which  gears  into  and  gives  motion 
to  the  segment  E.  Outside  of  the  pinion  is  the  scroll-wheel  C,  over  which  passes  the  flat-link  chain, 
carrying  the  weights  shown  in  Fig.  2197.  The  segment  E  vibrates  the  rock-shaft,  to  which  is  at- 
tached a  short  arm  for  lifting  the  valve,  where  the  governor  is  of  the  throttle  form.  When  the  gov- 
ernor is  to  be  applied  directly  to  the  cut-off,  the  long  arms  in  Fig.  2197  are  used. 



"  The  action  is  as  follows :  The  flanged  pulley,  being  driven  by  belt  from  the  main  shaft  of  the  en- 
gine, revolves  the  paddle-wheel  B.  As  the  oil  in  the  cylinder  offers  a  resistance  to  this  motion,  from 
being  held  by  the  ribs,  the  tendency  is  to  carry  the  cylinder  around  with  it.  The  weighted  chain  on 
the  wheel  C  prevents  this  until  the  velocity  of  the  paddle-wheel  has  reached  such  a  point  that  the 
friction  or  resistance  offered  by  the  oil  overcomes  the  inertia  of  the  weight,  when  the  cylinder  also 
begins  to  revolve,  and  the  pinion  D,  moving  the  segment  E,  closes  the  valve,  and  the  speed  is  re- 
duced, when  the  weights  again  bring  the  cylinder  back  to  its  original  position.  The  operation  is 
very  quick,  as  may  be  demonstrated  as  follows ;  The  paddle-wheel,  making  about  200  revolutions 
per  minute,  will  not  revolve  the  cylinder,  as  the  friction  of  the  oil  is  not  sufficient  to  overcome  the 
resistance  of  the  weight ;  but 



an  increase  of  a  very  few  rev- 
olutions on  the  speed  of  the 
paddles  will  instantly  move 
the  cylinder  at  nearly  the  same 
velocity.  Now,  as  the  slight- 
est motion  of  the  cylinder  is 
imparted  to  the  valve,  and  as 
about  two  revolutions  of  the 
former  will  entirely  close  the 
latter,  it  is  evident  that  the 
slightest  increase  of  speed  of 
the  engine  must  cause  the 
prompt  closing  of  the  valve. 

"The  power  which  the  gov- 
ernor is  capable  of  developing 
may  be  thus  demonstrated : 
Let  P  represent  the  power  re- 
ceived from  the  resistance  of 
the  oil  to  the  motion  of  the  paddles;  D  the  radius  of  the  pinion,  E  of  the  segment;  R  the  rock- 
shaft  arm  ;  IT  the  resistance  offered  by  the  valve ;  C  the  radius  of  the  cylinder.  Then  P  x  (C  —D) 
x  (E  —  R)  =  W.  Take,  for  illustration,  a  cylinder  8  inches  diameter,  with  a  pinion  (B)  1  inch  diam- 
eter; radius  of  segment  (E)  12  inches  to  pitch-line  of  teeth;  rock-shaft  arm  for  raising  valve,  1 
inch;  power  transmitted  to  cylinder,  15  lbs.  Then  15  x  (4  —  .5)  x  (12—  1)  =  577.5  lbs.  actual 
power  applied  to  valve." 

When  a  governor  regulates  an  engine  by  acting  on  the  throttle,  it  is  important  that  the  valve 
should  be  properly  designed.  Many  governors  that  were  otherwise  properly  proportioned  have 
failed  on  account  of  faulty  valves.  In  designing  a  governor,  the  object  to  be  fulfilled  is  that,  with  a 
given  variation  in  speed,  the  two  extreme  positions  of  the  governor  shall  correspond  to  a  complete 
closure  of  the  throttle  and  its  opening  to  the  fullest  extent ;  and  the  governor  should  be  sufficiently 
powerful  to  readily  overcome  all  resistance  to  motion.  While  rules  can  be  given  for  the  approximate 
determination  of  these  conditions,  it  is  only  by  careful  experiment  that  they  can  be  exactly  settled ; 
and  the  best  governors  in  the  market  are  the  result  of  practical  tests  by  their  manufacturers. 
Some  examples  of  ordinary  and  novel  forms  of  governors  are  appended. 

Fig.  2200  is  an  example  of  the  original  form  of  the  governor  as  introduced  by  Watt.  The  distin- 
guishing peculiarity  of  this  form  consists  in  the  connecting-links,  c  c,  being  situated  overhead,  and 
attached  to  the  arms  a  a  by  prolongations  of  the  latter,  which  pass  through  a  square  part  of  the 
upright  spindle  A,  to  which  they  are  both  jointed  by  one  pin.  When  at  rest  the  balls  are  usually 
received  into  arms  g  g,  curved  to  suit  their  surfaces,  by  which  means  the  rods  arc  relieved  from  all 
unnecessary  strain. 

Fig.  2201  is  a  representation  of  a  centrifugal  governor,  adapted  to  a  small  high-pressure  crank- 
overhead  engine.  In  this  species  of  engine  the  governor  is  usually  made  to  revolve  in  a  short  column 
B,  cast  in  a  piece  with  a  forked  bracket  embracing  the  crank-shaft,  and  its  spindle  A  A  is  driven  by 
a  pair  of  bevel-wheels  from  the  crank-shaft.  The  spindle  is  surmounted  by  a  double  brass  socket  b, 
attached  to  it  by  means  of  a  pin ;  and  to  this  socket  are  jointed  the  arms  a  a,  which,  as  well  as  the 
connecting-links  cc,  are  in  this  example  finished  in  the  lathe.  The  sliding  brass  socket  d,  to  which 
the  lower  ends  of  the  links  c  c  are  connected,  is  formed  with  a  groove,  into  which  is  inserted  the 
forked  end  of  a  lever  D,  having  its  centre  of  motion  in  a  small  wrought-iron  column  bolted  to  an 
arm  projecting  from  the  column  B.  From  the  opposite  end  of  this  lever  depends  the  slender  rod  e, 
connecting  it  immediately  with  the  throttle-valve  lever,  which  by  this  simple  construction  is  at  once 
made  to  rise  or  fall,  as  the  balls  collapse  or  diverge  in  obedience  to  the  varying  speed  of  the  engine. 

Fig.  2202  is  an  example  of  an  arrangement  of  the  pendulum  governor  sometimes  adopted  in 
highly-finished  engines.  The  peculiarity  of  this  form  consists  in  the  connecting-rod  e  being  attached 
directly  to  the  sliding  socket  d,  without  the  intervention  of  the  forked  lever.  For  this  purpose  the 
upper  portion  of  the  spindle  A  A  is  bored  out  truly  cylindrical,  to  a  point  somewhat  below  the  range 
of  the  sliding  socket  d.  This  last  is  attached  by  means  of  a  cotter  to  a  small  cylindrical  hollow  piece, 
which  fits  accurately  into  the  interior  of  the  spindle,  and  is  consequently  made  to  rise  and  fall  with 
the  socket  d,  a  long  slot  being  formed  in  the  spindle  to  allow  the  cotter  to  traverse  up  and  down. 
The  lower  end  of  the  rod  e  is  jointed  to  this  interior  piece  by  means  of  a  swivel,  so  as  to  rise  and  fall 
with  it,  without  being  affected  by  its  rotatory  motion.  At  the  top  of  the  governor-spindle,  the  rod 
e  is  guide  1  in  its  motion  by  being  made  to  pass  through  the  small  brass  vase  which  surmounts  the 
whole  apparatus ;  and  should  it  be  required  to  be  of  any  considerable  length,  the  necessary  rigidity 
may  be  imparted  by  fixing  a  weight  to  it,  as  shown  in  the  figure. 

In.  the  governor  represented  in  Fig.  2203,  the  vertical  spindle  A  A,  which  may  be  set  in  motion 



either  by  a  pulley  or  by  bevel-wheels  in  the  usual  manner,  is  surmounted  by  two  equal  horizontal 
arms  a  a,  furnished  with  stops  at  their  extremities.  The  governor-balls  run  freely  to  and  fro  upon 
these  arms  by  means  of  internal  friction-rollers,  and  are  drawn  toward  the  common  centre  in  the 
spindle  A,  by  means  of  cords  or  steel  ribbons  ii,  passing  over  two  pulleys  at  G,  and  attached  at 
their  lower  ends  to  the  sliding  collar  d,  in  which  works  the  forked  end  of  the  lever  I)  D,  which 
conveys  the  action  of  the  governor  to  the  throttle-valve.  A  spiral  spring  embracing  the  vertical 
spindle  presses  at  its  lower  extremity  against  the  Bliding  collar  d,  and  its  pressure  is  regulated  by  a 
sliding  stop  /«,  which  can  be  fixed  at  any  required  elevation  upon  the  spindle  by  a  set-screw.  The 
stop  h  having  been  set  so  as  to  cause  the  spring  to  press  down  the  collar  d  with  any  approved  force, 
and  the  throttle-valve  opened  to  any  required  extent,  the  engine  is  set  in  motion.  Should  its  speed 
exceed  the  stipulated  rate,  the  increased  centrifugal  force  will  cause  the  two  balls  to  diverge,  and, 
raising  the  collar  d,  will  partially  close  the  throttle-valve  and  diminish  the  supply  of  Bteam,  when, 
the  motion  being  checked,  the  spring  "ill  press  down  the  collar  and  cause  the  balls  to  collapse 
until  the  desired  rate  of  motion  is  obtained.  The  degree  of  force  exerted  by  the  spring  will  always 
require  to  be  adjusted  to  suit  the  nature  of  the  work  thrown  upon  the  engine,  because  a  small  quan- 
tity of  steam  only  will  be  required  when  the  work  is  light,  and  a  larger  quantity  when  it  is  heavy, 




while  the  speed  should  in  each  case  be  the  same ;  which  conditions  can  be  fulfilled  with  great  facility 
and  admirable  precision  by  the  use  of  this  kind  of  governor. 

Fig.  2204  represents  a  simple  and  compact  modification  of  the  centrifugal  governor.  Here  the 
balls,  instead  of  being  suspended  upon  arms  of  a  length  proportioned  to  the  velocity  at  which  the 
engine  is  required  to  move,  are  fitted  to  traverse  from  and  toward  their  common  centre  in  the 
spindle  A,  upon  the  arms  HH,  which  revolve  with  the  latter,  and  are  formed  into  circular  arcs  of  a 
curvature  determined  by  the  same  circumstances  with  the  length  of  the  suspending  arms  in  the  ordi- 
nary governor.  By  this  means  it  is  obvious  that  the  horizontal  plane  of  the  rotation  of  the  balls  will 
vary  with  the  varying  speed  of  the  engine,  in  precisely  the  same  way  as  in  the  conical  pendulum 
governor ;  and  the  vertical  motion  thus  generated  is  transferred  directly  to  the  sliding  socket  d, 
which  commands  the  throttle-valve  lever.  For  this  purpose,  it  is  necessary  that  each  of  the  balls 
should  be  made  in  halves  and  riveted  together  with  a  wrought-iron  pin,  as  shown  in  the  section,  Fig. 
2204  ;  a  space  being  left  between  the  hemispheres  to  admit  of  the  slotted  arms  a  a,  which  are  cast 
in  a  piece  with  the  sliding  socket  d,  and  through  which  the  connecting-pins  are  fitted  to  pass  freely, 
but  without  allowing  any  play. 

Another  variety  of  the  centrifugal  governor  is  represented  in  Figs.  2205  and  2206 ;  the  former 
being  a  sectional  elevation,  and  the  latter  a  plan  of  a  governor  constructed  by  M.  Bourdon  of  Taris, 
the  peculiarity  of  which  consists  in  the  axis  of  rotation  being  horizontal  instead  of  vertical.  The 
main  advantage  proposed  to  be  attained  by  this  system  is  the  more  convenient  transmission  of  the 
motion  of  the  prime  mover,  whether  by  wheel-work  or  by  pulleys.     The  principle  of  its  action  is  the 



same  as  that  of  the  common  governor.  The  spindle  A  A  is  of  cast-iron,  the  part  to  the  left  being 
hollow,  while  the  middle  portion  is  formed  into  a  species  of  open  framework,  inclosing  the  principal 
part  of  the  mechanism.  It  revolves  in  ordinary  plumber-blocks  B  B,  and  is  set  in  motion  by  the 
cone-pulley  C.  The  arms  a  a,  which  carry  the  governor-balls,  are  supported  upon  a  short  axis  work- 
ing on  the  points  of  two  steel  pins,  screwed  into  the  central  part  of  the  spindle  and  secured  by  jam- 
nuts  ;  this  axis  carries  also  a  toothed  sector  c,  working  into  a  similar  sector  upon  another  short  axis 
to  which  is  fixed  a  lever  d;  the  slender  connecting-rods  j  j,  traversing  the  hollow  part  of  the  spindle, 
and  supported  by  the  guides 

k  k,  serve  to  convey  the  mo-  _>^^%.  2205. 

tion  of  this  lever  to  the  throt- 
tle-valve gear,  which  is  pro- 
vided with  suitable  arrange- 
ments for  adjusting  the  ac- 
tion of  the  governor  upon  the 

The  object  of  the  arrange- 
ment, Figs.  2207,  2208,  and 
2209,  is  to  ring  a  bell,  and 
to  indicate  upon  a  dial  the 
velocity  of  rotation  of  mill- 
stones. This  mechanism  con- 
sists of  a  vertical  wrought- 
iron  axis  A  A,  revolving  in 
bearings  B  B,  bolted  to  the  wall  of  the  mill,  and  carrying  toward  its  upper  extremity  a  pulley  C 
which  receives  motion  from  the  main  driving-shaft.  To  this  axis  is  fixed  a  brass  socket  b,  to  which 
are  jointed  the  two  flat  arms  a  a,  terminated  by  the  governor-balls,  and  attached,  about  the  mid- 
dle of  their  length,  by  the  two  double  links  c  c,  to  the  sliding  socket  d,  made  in  halves  and  con- 
nected together  by  two  small  bolts.  To  this  latter  are  also  attached  the  two  slender  vertical 
rods  e  e,  which  traverse  the  pulley  C,  and  convey  the  action  of  the  governor  to  a  sliding  disk  D, 
provided  with  a  projecting  arm  or  catch,  of  such  length  as  to  come  into  contact,  should  the  machinery 
exceed  or  fall  short  of  its  proper  speed,  with  either  of  the  two  levers  //,  which  have  their  common 
centre  of  motion  in  a  short  vertical  axis,  and  are  attached  at  their  opposite  ends  by  slender  wires  to 
two  sockets  mounted  upon  a  horizontal  axis  K ;  each  of  these  sockets  carries  a  bell,  which,  by  the 
arrangement  described,  is  rung  when  the  catch  on  the  disk  D  strikes  either  of  the  levers  ff.  To 
the  sliding  socket  d  is  fixed  a  forked  rod,  having  one  of  its  branches  formed  into  teeth  like  a  rack ; 
this  rack  gears  into  a  small  pinion,  Fig.  2209,  carrying  upon  its  axis  an  index,  which  points  out  upon 
the  graduated  dial  F  the  speed  at  which  the  millstones  are  revolving.  Thus,  should  the  velocity  of 
the  prime  mover  relax,  the  vertical  axis  A  partaking  of  this  diminished  motion,  the  balls  collapse, 
the  socket  d  is  pressed  downward,  and  the  rack  causes  the  index  to  move  from  right  to  left.  The 
opposite  effect  is  produced  by  an  increase  of  the  speed  (these  different  positions  being  indicated  by 
the  dotted  lines  in  the  figure).  At  the  same  time  the  bell  is  sounded  by  the  apparatus  which  sur- 
mounts the  governor ;  and  the  attendant,  by  a  glance  at  the  dial,  is  made  aware  of  the  change  in  the 
velocity  of  the  machinery,  for  which  he  has  to  compensate  by  altering  the  degree  of  proximity  of 
the  upper  and  lower  stones.     It  is  well  known  that  the  action  of  the  governor  is  in  no  way  affected 



i  i\    i 

by  the  weight  of  the  balls,  further  than  that  these  should  be  made  of  a  size  proportionate  to  the 
resistance  to  be  overcome ;  accordingly,  in  the  case  now  before  us,  the  work  which  the  governor  is 
destined  to  perform  being  very  slight,  the  balls  may  be  made  of  extreme  lightness. 

The  air-reservoir  or  bellows  governor  is  an  apparatus  of  French  origin,  a  patent  having  been  granted 
to  the  inventor,  M.  Molinie  of  Saint-Pons,  in  1838.     The  principle  on  which  its  action  depends  con- 
sists in  causing  the  engine  to  force  a  quantity  of  atmospheric  air  into  a  reservoir  with  a  movable 
cover  through  which  the  air  escapes,  the  aperture  being  so  regulated  by  an  adjustable  valve  that  it 



shall  onlv  escape  at  a  given  rate.  Should  the  speed  of  the  engine  exceed  or  fall  short  of  the  pre- 
scribed limit,  the  air  is  forced  into  the  reservoir  faster  in  the  one  case  and  slower  in  the  other  than 
it  can  escape  through  the  valve;  consequently  the  movable  cover  is  raised  or  depressed,  and,  by 
means  of  suitable  connections,  partially  closes  or  opens  the  throttle-valve.  The  advantages  proposed 
by  this  system  are :  first,  greater  regularity  and  steadiness  of  action  than  is  attainable  by  the  com- 
mon governor,  combined  with  equal  delicacy;  and  secondly,  a  more  considerable  range  or  amount 
of  motion  available  for  the  purpose  of  regulation. 

Fig.  2210  is  an  external  elevation,  Fig.  2211  a  sectional  elevation  (on  a  plane  at  right  angles  to 
the  former),  and  Figs.  2212  and  221:;  sectional  plans  of  this  apparatus.  The  working  parts  are  in- 
closed within  a  cylindrical  vessel,  the  sole  being  formed  of  a  cast-iron  disk  A,  supported  upon  four 
small  columns  aa,  and  the  cover  of  a  cast-iron  capital  or  cornice  C ;  these  are  bound  together  by 
the  four  pilasters  B  B,  having  recesses  formed  on  their  edges  for  the  reception  of  cylindrical  sheet- 
iron  panels,  which  thus  admit  of  being  removed  at  pleasure  when  it  is  necessary  to  examine  or 
repair  the  internal  parts.  In  Figs.  2210  and  2211  these  panels  arc  shown  partially  removed.  Two 
small  wniught-iron  columns  I)  D  are  also  fixed  to  the  sole-plate,  and  serve  to  support  a  cylindrical 
cast-iron  vessel  /-',  the  bottom  plate  of  which  is  provided  with  two  apertures  guarded  by  the  flap- 
valves  d  and  //,  which  open  alternately  for  the  purpose  of  giving  admission  to  the  air  which  is  forced 
into  the  receiver  E  by  the  double  bellows  FF'\  these  are  respectively  supplied  with  air  from  the 




surrounding  atmosphere  by  the  apertures  b  and  /,  similarly  furnished  with  flap-valves,  the  former 
being  situated  in  the  sole-plate  A,  and  the  latter'  in  the  movable  piece  67;  the  stream  of  air  gen- 
erated in  the  lower  bellows  passing  through  the  upper  by  means  of  an  clastic  leather  tube  or  copper 
pipe  c.  The  cover  of  the  fixed  receiver  E  is  formed  of  a  movable  cylindrical  disk  //,  attached  to  the 
former  by  leather,  in  the  manner  of  an  ordinary  bellows,  and  thereby  admitting  of  being  elevated  or 
depressed,  according  to  the  degree  of  condensation  of  the  air  within  the  receiver;  this  is  regulated 
bv  means  of  a  small  conical  hole  //,  guarded  by  a  pointed  screw  ?',  properly  secured  from  turning, 
after  being  adjusted  so  that  the  air  forced  into  the  receiver  when  the  engine  is  at  its  normal  velocity 
shall  just  have  liberty  to  escape,  and  consequently  hold  the  movable  cover  suspended.  Motion  is 
communicated  to  this  apparatus  by  means  of  two  rods  //,  fixed  to  the  movable  intermediate  piece  67, 
and  attached  by  means  of  the  connecting-rods  m  m  to  cranks  formed  on  the  shaft  7,  which  is  set  in 
motion  by  a  belt  from  the  prime  mover  working  over  the  fast  and  loose  pulleys  J  J.  A  round  rod 
K,  screwed  into  the  movable  cover  //,  serves  to  convey  the  motion  generated  by  the  governor  to  the 
throttle-valve  or  sluice-gearing,  as  the  case  may  be.  On  this  rod  is  fixed  a  ball  X,  which,  for  the 
sake  of  adapting  the  governor  to  the  varying  circumstances  in  which  it  may  be  placed,  is  usually 
made  hollow  and  partially  filled  with  lead. 

Fig.  2214  is  a  representation  of  a  mode  employed  by  M.  Molinie  for  rendering  his  governor  most 
advantageously  applicable  to  regulating  the  supply  of  water  to  a  hydraulic  motor.  Besides  the  regu- 
lar sluice-gate,  he  makes  use  of  an  additional  valve  N',  to  which,  by  means  of  the  cord  and  pulleys 
shown  in  Fig.  2210,  he  attaches  the  governor.  The  face  of  this  valve  is  bent  into  a  cylindrical  form, 
and  it  is  jointed  by  rods  to  a  central  point  considerably  behind  the  sluice-face  0'.  By  this  means 
the  strain  arising  from  the  pressure  of  the  water  against  the  back  of  the  valve  is  counteracted,  and 
the  action  of  the  governor  rendered  sufficiently  delicate. 

Fis.  2215  represents  the  connection  of  this  governor  with  the  throttle-valve  of  a  steam-engine. 

The  efficient  operation  of  this  governor  depends  entirely  on  the  perfection  of  the  mechanism  by 



which  the  escape  of  the  air  from  the  receiver  E  is  regulated.  The  simple  contrivance  detailed  is 
altogether  inadequate,  as  it  is  neither  self-adjusting  nor  theoretically  perfect  in  any  circumstances, 
as  will  be  obvious  from  the  consideration  that  the  volume  of  any  fluid  escaping  by  a  given  orifice 
depends  not  only  on  the  section  of  that  orifice,  but  also  on  the  velocity  of  the  escape ;  so  that  the 
higher  the  velocity,  the  aperture  remaining  the  same,  the  greater  will  be  the  volume  of  issuing  fluid. 
To  compensate  for  this  circumstance,  M.  Molinie  devised  an  arrangement  at  once  simple  and  effec- 
tual. Instead  of  the  pointed  screw  i,  he  makes  use  of  a  conical  pin  i',  Fig.  2219,  which  is  attached 
by  nuts  to  the  movable  cover  H.  It  is  fitted  to  move  in  the  interior  of  a  brass  tube  h',  fixed  to  the 
stationary  part  of  the  air-receiver,  and  closed  at  the  bottom,  while  the  top  is  pierced  with  a  hole  of 
the  exact  size  of  the  thick  part  of  the  pin.  The  air  passes  by  an  adjustable  aperture  into  the  interior 
of  this  tube ;  and  according  as  the  cover  H  is  more  or  less  elevated  or  depressed,  the  area  of  the 
aperture  of  escape  is  proportionally  increased  or  diminished.  By  this  ingenious  contrivance,  not 
only  is  the  theoretical  defect  above  alluded  to  corrected,  but  a  great  additional  advantage  is  obtained 
in  the  more  rapid  and  energetic  action  of  the  governor. 

Figs.  2216,  2217,  and  2218  represent  two  different  modifications  of  the  vane  governor.     The  prin- 
ciple of  its  action  consists  in  the  atmospheric  resistance  to  rapid  motion  being  employed  to  counter- 
act the  force  of  gravity.     The  form  represented  in  Fig.  2216  is  that  which  illustrates  the  principle 
most  clearly.     On  the  crank-shaft  is  fixed  a  drum  or  pulley  0,  and  underneath  it,  or  in  any  con- 
venient situation,  is  placed  an  axis  carrying  a  small  grooved  pulley,  to  which  are 
attached  two  or  more  fans  or  vanes  PP.     The  former  communicates  motion  to 
the  latter  by  means  of  an  endless  band  or  belt,  which  is  also  passed  over  two 
friction-wheels,  the  first  of  which  is  attached  to  the  weighted  rod  r,  which  com- 
mands the  throttle-valve  lever  p,  and  the  other  to  a  gravitating  weight  q,  sus- 
pended freely  on  the  opposite  side  of  the  axis.     The  area  of  the  vanes  PP,  and 





the  weight  of  the  ball  q,  are  so  adjusted  in  relation  to  each  other  that  the  latter  is  just  sufficient  to 
drive  round  the  resisting  vanes  at  a  certain  velocity,  exactly  corresponding  with  the  normal  speed  of 
the  engine.  Any  increase  of  that  speed,  instead  of  accelerating  the  motion  of  the  vanes  (the  atmos- 
pheric resistance  being  nearly  uniform),  tends  to  raise  the  weight  and  diminish  the  supply  of  steam 
passing  through  the  steam-pipe  JY ;  and  any  relaxation  of  it  allows  the  weight  to  descend,  and 
thereby  opens  the  throttle-valve  in  a  corresponding  proportion. 

Figs.  2217  and  2218  are  a  side  and  end  elevation  of  an  arrangement  in  which  this  principle  is 
carried  out  in  a  more  practical  and  more  generally  applicable  form.  It  consists  of  an  upright  spindle 
s  s,  supported  in  suitable  bearings  in  a  cast-iron  standard  P,  placed,  in  the  usual  manner,  over  the 
crank-shaft  Q  of  the  engine,  upon  which  is  keyed  a  bevel-wheel,  driving  a  pinion  on  the  foot  of  the 
upright  spindle,  whereby  a  rapid  rotatory  motion  is  given  to  it.  The  upper  part  of  the  spindle  is 
formed  into  a  screw  or  worm,  the  threads  of  which  slope  at  an  angle  of  about  45°,  and  upon  which  a 
heavy  bush  or  nut  q  is  fitted  to  move  easily.  This  bush,  which  is  usually  formed  into  a  ball,  and 
corresponds  in  its  functions  with  the  suspended  weight  q  in  the  previous  example,  has  attached  to  it 
two  or  more  projecting  arms  furnished  with  vanes  P  P  ;  these  are  so  fitted  upon  the  arms  as  to  be 
capable  of  being  set  nearer  to  or  farther  from  the  spindle,  as  circumstances  may  require  ;  they  also 
admit  of  being  turned  upon  the  arms  in  an  oblique  direction,  as  shown  by  the  dotted  lines  in  Fig. 
2218,  in  order  to  diminish  the  atmospheric  resistance.  The  weighted  nut  is  connected  to  the  throttle- 
valve  by  means  of  a  double  link  and  swivel  A,  and  by  levers  and  rods  MM,  n  n,  in  the  usual  manner. 
From  the  above  description  it  will  be  seen  that  when  the  spindle  s  is  driven  in  the  direction  tending 
to  raise  the  nut  q,  the  latter  with  its  attached  vanes  will  be  carried  round  with  it,  and  at  the  same 
velocity,  until  and  so  long  as  the  resistance  of  the  air  against  the  vanes  corresponds  with  the  gravi- 
tating power  of  the  weighted  nut.  But  when  the  velocity  of  the  engine,  and  consequently  that  of 
the  spindle  s,  is  increased  beyond  that  point,  the  atmospheric  resistance  against  the  vanes  will  exceed 
the  gravitating  power  of  the  nut  and  its  mountings,  and  cause  them  to  ascend  upon  the  screwed 
spindle,  and  thus,  by  means  of  the  connecting-rods  and  levers  K L  M,  np,  will  diminish  the  supply 
of  steam  passing  through  the  steam-pipe  IV  to  the  engine.  If,  on  the  other  hand,  the  velocity  of  the 
spindle  is  reduced  below  that  required  by  the  resistance  of  the  vanes  to  overcome  the  gravitating 



tendency  of  the  nut  q,  the  latter  will  then  descend  upon  the  spindle,  and  thereby  increase  the  pas- 
sage for  the  supply  of  steam.  The  speed  of  the  engine  may  be  permanently  varied  at  pleasure,  by 
adjusting  the  vanes  upon  their  supporting  arms,  so  as  to  increase  or  diminish  the  gravitating  power 
of  the  nut  to  the  required  extent. 

The  chronometric  governor,  Figs.  2220  to  2223,  was  invented  by  Mr.  C.  W.  Siemens.  The  prin- 
ciple of  its  action  appears  to  be  an  admirable  and  perfect  one,  involving  as  it  does  the  happy  idea  of 
so  combining  the  invariable  motion  of  an  independent  pendulum  with  the  varying  speed  of  the  engine 
or  other  motor,  as  to  make  the  former  correct  instantaneously  the  fluctuations  of  the  latter.  Fig. 
2220  is  an  elevation,  and  Fig.  2222  a  section  of  this  apparatus,  which  is  set  upon  a  bracket  SS 
bolted  to  the  wall  of  the  engine-house,  and  supported  by  a  framework  T  T,  consisting  of  four  small 
columns  and  a  circular  entablature.  The  differential  velocity  between  the  engine  and  the  revolving 
pendulum  Y  is  obtained  by  means  of  the  three  bevel-wheels  t,  u,  and  v  ;  this  last  is  firmly  connected, 
by  an  upright  spindle  and  grooved  arm  w,  with  the  upper  extremity  of  the  pendulum,  produced 
through  the°  ball-and-socket  joint  which  forms  its  point  of  suspension  and  revolution.  The  under 
wheeH  is  fixed  to  the  pulley  U,  which  is  driven  by  the  engine  with  its  uncertain  velocity,  and  in  the 
contrary  direction  to  the  motion  of  the  wheel  v.  Both  these  wheels  move  in  gear  with  the  third 
bevel-wheel  w,  which  runs  perfectly  free  upon  its  axis,  and  is  also  permitted  to  travel  round  the 
perpendicular  socket  forming  the  bearing  of  the  others.     It  is  obvious  that  if  t  and  v  revolve  in 





contrary  directions,  but  with  equal  velocities,  the  wheel  u  will  also  revolve  on  its  axis,  but  will  not 
change  "its  angular  position;  while  any  difference  in  speed  between  t  and  v  will  cause  the  wheel  u  to 
follow  the  direction  of  the  faster,  which  will  at  once  alter  the  supply  of  steam,  the  arm  x  being  at- 
tached to  the  throttle-valve  contained  within  the  steam-pipe  iV7,  by  means  of  the  lever  and  adjustable 
connecting-rod  p  and  y.  Another  arm  attached  to  the  axis  of  the  wheel  w,  on  the  opposite  side  of 
the  perpendicular  socket,  is  connected  by  means  of  the  rod  z  to  a  lever  working  between  two  adjust- 
able stops  Z  Z,  which  serve  to  confine  the  range  of  the  throttle-valve  within  convenient  limits.  To 
maintain  the  motion  of  the  pendulum  a  constant  power  is  required,  resembling  that  of  the  falling 
weight  in  an  ordinary  clock.  This  power  is  supplied  by  the  weight  r,  which  tends  constantly  to  pull 
the  wheel  u  to  one  side ;  and  this  strain,  being  borne  equally  by  the  wheels  t  and  v,  causes  the  latter, 
and  with  it  the  pendulum  Y,  to  revolve,  while  the  former,  revolving  in  the  contrary  direction,  is  con- 
stantly engaged  to  raise  the  weight  back  again  into  its  proper  position.  In  practice  it  has  been 
found  that  the  power  necessary  for  maintaining  the  action  of  the  pendulum  is  much  less  than  that 
required  to  effect  the  movement  of  the  valve  ;  and  accordingly  Mr.  Siemens  has  adopted  the  principle 
of  driving  the  pendulum  with  an  excess  of  power,  which  shall  be  neutralized  by  friction  apparatus 
when  not  wanted,  and  shall  be  allowed  to  act  freely  when  the  governor  requires  its  assistance  to 
move  the  valve.  This  is  effected  as  follows :  Surrounding  the  grooved  arm  w  is  situated  a  conical 
ring  ir,  cast  with  the  framing  T  T,  and  accurately  bored  out ;  against  the  interior  of  this"  absorb- 
ing ring"  a  small  piece  of  steel  accurately  fitted  into  the  open  end  of  the  grooved  arm  w  is  pressed 
by  the  short  end  of  the  pendulum  rod  A',  a  spring  being  interposed  for  the  purpose  of  letting  the 



pressure  come  on  gradually.  It  is  evident  that  whenever  there  is  an  excess  of  driving  weight  which 
causes  divergence  in  the  axis  of  rotation,  the  surface  of  the  steel  rubber  and  of  the  fixed  ring  will 
be  pressed  together  with  a  force  exactly  sufficient  to  balance  the  excess  ;  and  so  soon  as  the  pendu- 
lum falls  back  toward  a  smaller  arc  of  rotation,  it  will  relieve  the  friction  apparatus,  and  permit  an 
increased  supply  of  power  to  overcome  the  resistance  of  the  valve.  A  second  spiral  spring  is  laid 
within  the  grooved  arm  w,  behind  the  point  of  the  pendulum,  for  the  purpose  of  preventing  the 
latter  from  dropping  into  its  perpendicular  position,  and  to  facilitate  its  starting  with  the  engine. 
The  adjustment  of  the  valve  is  effected  at  the  very  instant  that  the  equilibrium  between  the  power 
and  load  is  disturbed ;  an  advance  of  one-fiftieth  of  a  revolution  of  the  fly-wheel  is  found  sufficient  to 
close  the  valve  entirely.  By  converting  the  friction  apparatus  into  a  regular  brake,  the  power  of 
the  governor  may  be  increased  ;  and  in  this  way  it  may  be  applied  for  the  regulation  of  water-wheels, 
and  such  steam-engines  as  are  furnished  with  variable  expansion  gear,  which  are  better  regulated  by 
increasing  or  diminishing  the  amount  of  expansion  than  by  throttling  the  steam. 

Fig.  2224  represents  Silver's  marine  governor.  A  A'  are  loaded  arms  pivoted  in  their  centres  at 
B  to  the  shaft  C,  which  receives  motion  in  any  suitable  manner  from  the  engine.  The  arms  A  A' 
are  connected  together  through  the  medium  of  the  sliding  sleeves  D  D,  the  sleeve  D  being  united  to 
arms  A  A'  by  means  of  the  rods  E  E',  and  sleeve  B'  by  means  of  the  rods  E E.  F E  are  brackets 
on  the  arms  A  A',  to  which  the  ends  of  the  rods  EE  are  attached.  These  brackets  are  placed  at  an 
angle  of  45°,  so  that  the  line  of  draught  of  the  arms  and  rods,  when  the  balls  fly  out,  is  always  paral- 
lel to  the  shaft  C.     The  centrifugal  force  of  the  balls  is  counteracted  by  the  employment  of  a  spiral 

spring  /,  to  which  the  sleeve  D  is  attached  by  means  of  clamps  G.  The  tension  of  the  spring  is 
increased  or  diminished  at  pleasure  by  turning  the  nut  J,  which  moves  the  claw-collar  K  out  or  in, 
thus  rendering  the  governor  accordingly  more  or  less  sensitive,  as  desired.  The  collar  K  terminates 
in  a  screw  on  which  the  nut ./  moves.  When  motion  is  communicated  to  the  spindle  by  the  engine, 
the  balls  will  have  a  tendency  to  fly  out  in  the  direction  of  the  arrows,  and  to  move  the  sleeves  D  D' 
laterally.  The  sleeve  D  is  furnished  with  a  collar  H,  which  is  grasped  by  a  forked  crank  M,  pivoted 
to  the  standard  0.  The  lower  branch  of  the  lever  JY  is  connected  with  a  rod  leading  to  the  throttle- 
valve.  The  connection  and  operation  of  the  sleeve  D'  on  the  throttle-valve  are  similar  to  those  of 
ordinary  governors,  and  require  no  particular  description. 

There  are  various  other  forms  of  marine  governors,  but  the  majority  of  them  act  on  a  principle 
somewhat  similar  to  Silver's,  Fig.  2224,  or  to  Huntoon's,  Fig.  2217.  For  accounts  of  several  marine 
governors,  and  discussions  of  the  subject,  see  "Transactions  of  the  Society  of  Engineers,"  1863; 
"  Transactions  of  the  Institution  of  Engineers  in  Scotland,"  v.,  xii. ;  and  "  Proceedings  of  the  Insti- 
tution of  Mechanical  Engineers,"  1866.  Ii.  H.  B. 

GRAIN-DRILLS.     See  Agricultural  Machinery. 

GRAIN-MILLS.     See  Mills,  Grain. 

GRAPHITE  (also  termed  plumbago  and  black  lead,  the  latter  an  incorrect  title,  the  substance  not 
containing  lead  in  any  form).  A  mineral  consisting  of  from  90  to  95  per  cent,  carbon,  with  traces 
of  iron,  silica,  alumina,  lime,  and  magnesia.  It  was  formerly  supposed  to  be  the  carburet  of  iron, 
from  traces  of  iron  found  in  many  of  the  deposits ;  but  iron  and  other  impurities  are  only  mechani- 
cal admixtures,  no  combination  of  graphite  and  iron  or  other  substance  having  yet  been  found.  It 
is  found  in  nature  in  both  a  crystalline  and  an  amorphous  condition,  opaque,  of  a  metallic  steel-gray 
color  and  lustre,  a  greasy  unctuous  feel  when  rubbed  between  the  fingers,  and  giving  a  peculiar  shiny 


streak  on  paper.  Its  specific  gravity  is  2.09,  rising  somewhat  above  this  as  impurities  increase.  Its 
hardness  ranges  between  1  and  2.  Crystallized  graphite  occurs  in  six-sided  tables,  belonging  to  the 
hexagonal  system,  cleaving  perfectly  in  the  direction  of  the  base,  and  having  the  basal  planes  striated 
parallel  to  the  alternate  sides ;  but  the  mineral  is  more  commonly  found  in  foliated  or  granular  form. 

The  black  lead  of  commerce,  and  what  is  so  called  by  the  trade  in  first  hands,  is  found  principally 
in  Bavaria  and  Austria.  The  plumbago  of  commerce  comes  mainly  from  the  island  of  Ceylon,  but  is 
found  in  many  parts  of  the  United  States,  being  mined  successfully,  however,  only  at  Ticonderoga  in 
the  State  of  New  York.     It  is  also  mined  to  a  small  extent  in  the  Ottawa  region  of  Canada. 

Plumbago  is  very  refractory.  A  piece  with  sharp  projecting  angles  has  been  subjected  for  two 
hours  to  a  heat  that  would  melt  steel,  and  on  cooling  the  sharpest  points  were  found  perfect ;  but  it 
will  exhaust  if  left  on  top  of  such  a  fire.  It  is  found  in  veins  in  a  pure  state,  is  removed  in  lumps, 
and  a  selection  of  these  forms  the  "  prime  lump  "  of  commerce.  The  formation  most  common  in  the 
pure  state  is  that  of  laminated  crystals,  elongated  at  right  angles  with  the  sides  of  the  vein,  if  not 
more  than  from  4  to  6  inches  wide;  but  when  the  vein  widens  the  crystallization  often  radiates  from 
numerous  centres,  and  the  whole  formation  is  very  beautiful.  The  foliated  variety  is  equally  valuable 
and  more  brilliant,  but  rare  in  any  quantity.  The  acicular  form  of  crystal  is  not  apt  to  be  as  pure 
in  the  lump,  but  is  useful  for  most  purposes.  The  granulated  variety,  the  purest  of  all,  is  of  little 
use  for  crucibles,  but,  with  suitable  manipulation,  produces  the  finest  grades  for  electrotyping  and 
fine  lead  pencils.  Pure  plumbago  is  absolutely  free  Erom  grit  when  pulverized  and  rubbed  between 
the  fingers;  and  the  polish  produced  in  the  same  way  is  instantaneous  and  very  bright,  being  like  a 

darker  shade  of  polished  silver.     It  is  also  found  mixed  with  ir rhomb  spar  and  other  forms  of 

lime,  the  rock  and  earth  in  which  the  vein  is  carried,  and  many  Other  foreign  substances  injurious 
for  all  the  purposes  for  which  pure  plumbago  is  needed;  so  that  much  care  is  necessary  in  pur- 
chasing the  raw  material  for  a  given  purpose.  Lime,  for  instance,  is  fatal  to  plumbago  for  crucible- 
making.  The  plumbago  mined  in  the  interior  of  the  island  of  Ceylon  is  brought  down  to  Colombo 
in  bullock-carts.  It  is  there  selected  into  grade- ;  so  much  as  may  be  finely  broken  up  is  sifted,  and 
the  coarser  part  of  this  is  called  "chips,"  while  the  finer  part  is  called  "dust."  The  "  dust "  from 
prime  lump  is,  of  course,  very  different  in  character  from  the  dust  left  from  the  poorer  grades  of 
lump;  and  all  of  it,  whether  "lump  or  dust,  after  being  handled  and  packed  in  barrels  in  Colombo, 
becomes  so  black  and  bright,  by  the  poor  particles  rubbing  against  the  good,  that  the  touch  of  an 
expert  is  required  to  distinguish  between  the  grades.  The  system  adopted  at  Ticonderoga,  by  the 
Dixon  Company,  is  to  separate  the  mineral  from  its  Impurities  by  crushing  and  washing  by  the 
huddle  process,  and  sizing  the  particles  lor  different  uses  by  floating  in  water. 

The  German  black  lead  is  not  refractory,  and  is  therefore  useless  lor  any  purpose  that  brings  it  in 
contact  with  fire.  It  has  no  value  for  the  crucible-maker  or  for  stove-polish,  and  is  of  but  little 
use  as  a  lubricator.  It  has  a  very  low  conducting  power  even  in  its  pure  state,  and  the  best  quality 
that  comes  to  market  is  far  from  pure.  None  of  it  comes  in  its  original  state  as  mined,  but  all  of  it 
is  washed  and  floated,  and  so  the  grades  are  produced.  In  fact,  it  resembles  a  weak  blade  clay  more 
nearly  than  it  does  true  plumbago,  in  nature  as  well  as  in  appearance.  It  is  used  often  on  account 
of  its  cheapness,  when  it  would  be  cheaper  to  use  the  real  plumbago  even  at  five  times  the  price. 

The  most  important  applications  of  graphite  are  to  the  manufacture  of  lead  pencils  (see  Lead 
Pencils)  and  crucibles  (see  Crucibles).     It  is  also  made  into  stove-polish,  for  which  purpose  only 

the  best  quality  of  graphite  Bhould  be  used;  and  the  finer  it  is  pulverized  the  better,  as  each  particle 
should  be  mi  small  that  it  flattens  out  at  once  on  the  iron,  adheres  to  it,  and  polishes  quickly,  while 
larger  particles  will  fly  off  and  be  wasted,  a-  well  as  creating  a  dust  and  requiring  more  labor  to  pro- 
duce a  fine  polish.  The  polish  from  pure  foliated  plumbago  will  last  on  the  iron  for  a  long  time, 
while  that  from  German  black  lead  will  burn  a  reddish  brown  when  the  stove  is  raised  to  a  red  heat. 

Graphite  is  also  used  for  lubricating,  and  when  so  employed  Bhould  be  exceedingly  line  and  abso- 
lutely pure.  For  hlowing-cvlinders,  the  best  quality  of  Ticonderoga,  pulverized  to  the  finest  grade, 
pure  and  left  with  a  good  "body,  is  the  most  economical.  For  engines,  rolling-mills,  and  machine- 
bearings,  the  very  finest  should  always  be  used.  For  wood  bearings,  after  oiling  with  the  plumbago 
a  few  Times,  the  oil  can  be  dispensed  with,  and  the  pure  plumbago  only  applied  in  the  dry  powder. 
For  metal  bearings  it  should  be  freely  mixed  with  oil.  On  hot  axles  or  journals  apply  it  freely  dry, 
and  then  oil  up  as  usual.    (See  Lubricants. ) 

Graphite  is  employed  in  electrotyping  (see  Electro-Metallurgy);  as  a  facing  for  moulds;  by 
piano-makers  for  coa'ting  the  bridge  over  which  the  wires  are  drawn,  to  prevent  the  wires  from  ad- 
hering to  the  wood  ;  by  organ-builders  to  lubricate  the  slides  ;  by  hatters  to  impart  a  peculiar  tone 
to  the  colors  and  a  softness  and  smoothness  to  felt  hats  ;  by  glass-makers  for  coloring  dark  glass  for 
bottles,  etc. ;  as  a  body  for  paint  which,  is  both  water-  and  fire-proof;  for  coating  the  bottoms  of 
boats ;  and  for  polishing  gunpowder  (see  Exr-LOSiVF.s)  and  shot.  It  is  also  combined  in  a  refractory 
mixture  for  tuveres,  pointing  up  furnaces,  etc.  This  is  composed  of  equal  parts  of  Dutch  pipe-clay, 
fire-clay,  half  the  quantity  (by  measure,  not  weight)  of  charcoal,  and  the  same  half  quantity  of  silica 
(pure  quartz  sand,  srround  fine,  being  the  best);  to  this  mixture  add  as  much  of  the  plumbago  as 
possible,  and  leave  the  mass  thin  enough  to  work.  It  should  be  made  just  thin  enough  with  water, 
so  that  it  will  run  rather  sluggishly.  u-  "■ 

GRAVER.     See  Lathe-Tools,  Turning. 

GRAVITATION,  UNIVERSAL.     See  Dynamics. 

GRAVITY,  MEASURE  OF.     See  Dynamics. 

GRAVITY,  SPECIFIC*  The  ratio  of  the  weight  of  one  body  to  that  of  an  equal  volume  of 
another,  adopted  as  a  standard  of  reference.  For  solids  and  liquids  the  standard  is  pure  water,  at  a 
temperature  of  60°  F.,  the  barometer  being  at  30  inches.     Air  is  the  standard  for  aeriform  bodies. 

*  From  the  "  American  Cyclopaedia." 



A  cubic  foot  of  water  weighing  1,000  oz.,  if  the  same  bulk  of  another  substance,  as  for  instance  cast- 
iron,  is  found  to  weigh  7,200  oz.,  its  proportional  weight  or  specific  gravity  is  7.2.  It  is  convenient 
to  know  the  figures  representing  this  proportion  for  every  substance  in  common  use,  that  _the_  weight 
of  any  given  bulk  may  be  readily  determined ;  and  for  all  substances  the  specific  gravity  is  used 
among  other  tests  for  the  purpose  of  distinguishing  bodies  from  each  other,  the  same  substance  being 
found,  under  the  same  circumstances,  to  retain  its  peculiar  proportional  weight  or  density.  Hence 
tables  of  specific  gravity  are  prepared  for  reference,  and  in  every  scientific  description  of  substances 
the  specific  gravity  is  mentioned.  In  practical  use,  the  weight  of  a  cubic  foot  is  obtained  from  the 
figures  representing  the  density  by  moving  the  decimal  point  three  figures  to  the  right,  which  ob- 
viously from  the  example  above  gives  the  ounces,  and  these  divided  by  16  the  pounds  avoirdupois, 
in  the  cubic  foot. 

Different  methods  may  be  employed  to  ascertain  the  specific  gravity  of  solids.  That  by  measuring 
the  bulk  and  weighing  is  rarely  practicable,  nor  is  it  desirable.  As  a  body  immersed  in  water  must 
displace  its  own  bulk  of  the  fluid,  the  specific  gravity  may  be  ascertained  by  introducing  a  body,  after 
weighing  it,  into  a  suitable  vessel  exactly  filled  with  water,  and  then  weighing  the  fluid  which  is  ex- 
pelled. ^Th'e  proportional  weight  is  then  at  once  obtained.  Wax  will  cause  its  own  weight  of  water 
to  overflow;  its  specific  gravity  is  then  1.  Platinum,  according  to  the  condition  it  is  in,  will  cause 
only  from  ^  to  vttt  of  its  weight  of  water  to  escape,  showing  its  specific  gravity  to  be  from  21  to 
21.5.  But  a  more  exact  method  than  this  is  commonly  employed.  The  difference  of  weight  of  the 
same  substance,  weighed  in  air  and  when  immersed  in  water,  is  exactly  that  of  the  water  it  displaces, 
and  mav  consequently  be  taken  as  the  weight  of  its  own  bulk  of  water.  The  specific  gravity  then  is 
obtained  by  weighing  the  body  first  in  air,  and  then,  suspended  by  a  fibre  of  silk  or  a  hair,  in  water, 
and  dividing  the  weight  in  air  by  the  difference.  If  the  body  is  lighter  than  water,  it  is  to  be  at- 
tached to  one  heavier,  to  make  it  sink  ;  then  find  the  loss  of  the  two  by  immersion,  and  also  the  loss 
of  the  heavier  body ;  the  difference  will  express  the  weight  of  water  displaced  by  the  lighter  body, 
whose  weight  divided  by  this  difference  will  give  its  specific  gravity.  It  is  hardly  necessary  to  say 
that  the  substance  examined  must  be  free  from  mixture  of  foreign  matters,  and  especially  from 
cavities  that  may  contain  air.  Minerals,  if  suspected  to  contain  such,  should  be  coarsely  pulverized, 
and  then  the  second  method  above  may  be  conveniently  applied  to  determine  their  density.  The 
specific  gravity  of  fine  powders  may  be  determined  by  one  of  the  methods  employed  for  ascertaining  the 
specific  gravity  of  fluids,  viz. :  by  comparing  the  weight  of  a  measured  quantity  with  that  of  the  same 
quantity  of  water.  A  glass  vessel  called  a  specific-gravity  bottle  is  commonly  employed,  which  is 
furnished  with  a  slender  neck,  upon  which  is  a  mark"  indicating  the  height  reached  by  1,000  grains 
of  water.  The  substance  to  be  examined  is  introduced  till  it  reaches  the  same  mark,  and,  the  weight 
of  the  empty  bottle  being  known,  only  one  weighing  is  required  to  obtain  the  result. 

A  common  method  for  finding  the  specific  gravity  of  fluids  is  by  the  instrument  called  a  hydrome- 
ter or  areometer,  of  which  several  kinds  are  in  use,  all  dependent  on  the  principle  that  the  weights 
required  to  immerse  a  light  body,  as  a  bulb  of  glass,  in  different  fluids,  are  proportional  to  the 
densities  of  these  fluids.  "Such  instruments  are  used  for  ascertaining  the  specific  gravity  of  liquors, 
as  an  indication  of  their  strength.  (See  Hydrometer.)  Gaseous  bodies  are  weighed  in  a  thin  glass 
flask  or  other  vessel  made  for  the  purpose,  and  provided  with  a  stop-cock.  The  vessel  is  exhausted 
of  air  before  the  introduction  of  the  gas.  The  experiment  requires  particular  care,  as  the  result  will 
be  found  to  vary  under  different  conditions  of  pressure,  temperature,  and  the  hygrometric  state  of 
the  atmosphere.  The  temperature  of  the  air  should  be  60°  and  barometric  pressure  30  inches.  The 
specific  gravities  may  also  be  calculated  from  the  atomic  weights  of  the  gases :  when  the  atomic 
volume  is  equal  to  tliat  of  hydrogen,  it  is  obtained  by  multiplying  the  specific  gravity  of  hydrogen  by 
the  atomic  weight  of  the  gas ;  when  the  atomic  volume  is  half  that  of  hydrogen,  the  specific  gravity 
of  the  gas  is  equal  to  the  specific  gravity  of  hydrogen  multiplied  by  twice  the  atomic  weight  of  the 
gas ;  and  when  the  atomic  volume  is  twice  that  of  hydrogen,  the  specific  gravity  of  the  gas  is  equal 
to  the  specific  gravity  of  hydrogen  multiplied  by  half  the  atomic  weight  of  the  gas. 

The  proportions  of  two  ingredients  in  a  compound,  as  in  an  alloy  of  gold  and  silver,  may  be  found 
by  multiplying  the  specific  gravity  of  each  ingredient  by  the  difference  between  it  and  the  specific 
gravity  of  the  compound.  As  the  sum  of  the  products  is  to  the  respective  products,  so  is  the  specifio 
gravity  of  the  body  to  the  proportions  of  the  ingredients ;  then  as  the  specific  gravity  of  the  com- 
pound is  to  the  weight  of  the  compound,  so  are  each  of  the  proportions  to  the  weight  of  its  material. 

The  following  table  presents  the  specific  gravities  of  substances  most  likely  to  be  referred  to,  col- 
lected from  various  sources.  The  weight  of  a  cubic  foot  in  ounces  avoirdupois  is  seen  by  moving 
the  decimal  point  three  figures  to  the  right. 

Acid,  acetic 1 .062 

arsenic 3.391 

boracic,  crystallized 1 .  479 

boracic,  fused 1 .  803 

citric V  1.034 

hydrochloric 1.200 

nitric 1.271  to  1.583 

aqua  rejria 1 .234 

phosphoric,  liquid 1 .  558 

phosphoric,  solid 2.800 

sulphuric 1 .841 

Alabaster 1 .874 

Alcohol,  absolute 0.792 

of  commerce 0.835 

Ale  or  beer 1.085 

Alum 1 .  724 

Aluminum 2.560  to  2.670 

Table  of  Specific  Gravities. 

Amber 1.064  tol. 100 

Ambergris 0 .780  to  0 .926 

Amethyst,  common 2.750 

oriental,  or  violet  sapphire, 

3.309  to  4.160 

Ammonia 0.875 

Anthracite 1 .360  to  1 . 850 

Antimonv 6.7<>2 

Asphaltu'm 0.905  to  1.650 

Barytes 4.000 

"sulphate  of  (heavy  sparl 

4.300  to  4.720 

Basalt 2.864 

Beeswax 0.956  to  0 .964 

Bismuth 9.822 

Brandy 0.837 

Brass 7.S24  to  8.396 


Bronze,  gun-metal . . 

1.900  to  2.000 







....      S.998 


1. 930 

Coal,  bituminous. . . . 

...1.020  to  1.350 







.  2.540  to  2.850 



Diamond 8.521  to  3.550 

Dolomite 2.540  to  2.S30 

Earth,  mean  of  the  globe 5.210 

Emerald 2. 678  to  2.775 

Ether,  sulphuric 0.632  to  0.775 

Fat  of  beef 0.923 

Feldspar 2 .400  to  2 .620 

Freestone 2.143 

Garnet 3.150  to  4.800 

Glass,  bottle 2.783 

crown 2 .  520 

green 2 .  042 

Hint 2.760  to  8.329 

plate 2.760 

plate  of  St.  Gobain 2.4-b 

Gold,  native 15.600  to  10.500 

pure,  cast 19.253 

hammered 19.862 

coin 17.647 

22  carats  flue 17 .4^0 

20  carats  fine 15.709 

Granite,  Quincv 2.652 

States  Island 2.780 

Graphite 1.987to2.400 

Grindstone 2.148 

Gunpowder,  loose 0.830  to  0.900 

close  shaken 0.987 tol. 000 

solid 1.550  to  1.800 

Gum  arable 1.452 

Gypsum,  compact. ...  i  .s72  to  2.288 
Heliotrope  or  bloodstone, 

2.680  to  2.700 

Hematite  iron  ore 4 .500  to  5.300 

Honey 1.456 

Hyacinth 4.000  to  4.750 

Ice 0.980 

Iodine 4.943 

Indium,  hammered 28.000 

Iron,  malleable 7.615  to  7.-17 

cast 7.207 

ore,  magnetic 4.9l)0  to  5.200 

Ivory 1.822  to  1.917 

Lard 0.047 

Lead,  cast 11 .350  to  11 .445 

white 7.285 

ore.  galena 7.250  to  7.780 

Lime,  quick ■■■     0.804 

Limestone,  compact..  2.380  to  3.000 

crystallized 2.722 

Magnesia,  carb 2.222  to  2.612 

Malachite 3.700  to  4.000 

Manganese  ore  (psilomclane). 

3.700  to  4.330 
Marble,  Carrara 2.716 

Parian 2.887 

Egyptian 2.668 

Mercury,  common 18.568 

pure 14.000 

Mica 2.750  to  3.100 

Milk 1.032 

Myrrh 1.360 

Naphtha 0.700  to  0.847 

Nickel,  cast 8.279 

Nitre  (saltpetre) 1.900 

Gil.  castor 0.970 

linseed  0.940 

olive 0.91B 

turpentine 0.870 

whale 0.928 

Gpal 2.114 

Opium 1.887 

Palladium n  .800 

Pearl,  oriental 2.510  to  2.750 

Peruvian  bark 0.784 

Pewter 7.471 

Phosphorus l  .770 

Platinum,  native...  17. i  to  18.000 

refined 19  500 

hammered 20.886 

v\irc '-'I  .041 

laminated 22.069 

Porcelain,  China 2.886 

Porcelain,  Sevres 2 .  145 

Porphyry 2.458  to  2.072 

Potassium 0.865 

Proof  spirit 0.923 

Quartz 2. .Mm  to  'J. sun 

Rhodium 11 .000 

Rosin 1.100 

Ruby 4.283 

Salt,  common 2.180 

Sand 1.500  to  1  ,800 

Sapphire,  oriental 8.994 

Serpentine 2.507  to  2.591 

Silver,  pure,  cast 10.474 

hammered 10.510 

coin 10.584 

Slate 2.110  to  2.672 

Soapstone 2 .t'50  to  2 .800 

Sodium 0.972 

Spermaceti 0.943 

Steel,  hard 7.816  to  7.840 

soft 7  388 

Sugar 1.606 

Sulphur,  native 2.088 

fused 1.990 

Tallow 0.941 

Tar 1.015 

Tellurium 5.700  to  6.115 

Tin,cast 7.291 

hardened 7.299 

Topaz 3 .4(10  to  3 .650 

Tourmaline 2.940  to  8.800 

Tungsten 17.400 

Tunpioise 2.600  to  2.880 

Ultramarine 2.862 

Vinegar 1  013  to  1.0-0 

Water,  distilled 1. I 

sea 1.028 

Dead  Bea 1.240 

Wine,  Burgundy 0.991 

white  champagne 0.997 

Zinc,  cast 7.190 

GRINDING.    See  Emery-grinding  and  Grindstones. 

GRINDSTONES.  Grindstones  are  used  for  giving  a  cutting;  edge  to  implements  and  tools,  and 
also  for  removing  by  abrasion  the  surface  of  metal  to  prepare  the  same  for  painting  or  for  polishing 
processes.  The  English,  Nova  Scotia,  and  Ohio  grindstones  are  principally  used;  but  each  of  these 
varieties  is  subdivided  into  different  sizes  and  kinds  of  grit,  the  most  prominent  of  which,  and  the 
work  for  which  they  are  adapted,  are  as  follows  :  Newcastle— Yellow  color  and  sharp  grit:  the  fine 
soft  ones  for  grinding  saws,  and  the  coarser  and  harder  ones  for  sad-irons  and  springs,  for  bead 
and  face  stones  in  nail  works,  and  for  castings  (dry  grinding).  Wickeraly — Grayish  yellow  color: 
for  grinding  saws,  squares,  bevels,  and  cutlers1  work  generally.  A  very  soft  grit  to  avoid  taking  out 
the  temper.  Liverpool  (or  Mellinff) — Of  a  red  color  and  very  sharp  gril  :  for  saws  and  edge-tools 
generally.  An  excellent  «grit  for  sharpening  axes  in  ship-yards.  Nova  Scotia — Blue  or  yellowish 
gray  color,  and  of  all  grits,  from  the  finest  and  hardest  to  the  coarsest  and  softest:  the  large  ones 
for  grinding  sad-irons  and  hinges,  springs,  and  edge-tools  ;  the  medium  and  small  sizes  for  machine 
shops  and  for  sharpening  edge-tools  generally.  Bay  Wialeur,  X.  B.—Ot  a  uniform  blue  color,  and 
soft,  sharp  grit:  for  table-cutlery,  and  admirably  adapted  for  machinists'  tools,  and  for  sharpening 
edge-tools  generally,  when  a  fine  edge  is  required.  Berea — White  color,  fine  and  sharp  grit :  for 
sharpening  edge-tools  generally.  Amherst  {Black  River) — Brownish-white  color,  soft,  loose  grit :  for 
edge-tools,  and  the  very  soft  ones  for  saws.  Independence — Grayish-white  color,  and  coarse  sharp 
grit :  for  grinding  springs  and  files,  and  for  dry  grinding  of  castings.  MassiUon — Yellowish  white 
color,  coarse,  sharp  grit:  for  edge-tools,  springs,  files,  and  nail-cutters'  face-stones,  and  for  dry 
grinding  of  castings.  Huron  (Michigan)— 01  a  uniform  blue  color,  and  fine,  sharp  grit:  good  for 
sharpening  tools  when  a  very  fine  edge  is  required.  Glass- Cutters'  Grindstones,  of  Newcastle,  'War- 
rington, Craigleith,  and  Yorkshire  grits :  for  checkering,  mitering,  fluting,  and  for  punty  stones. 
Curriers'  Rubstones,  of  Newcastle,  Nova  Scotia,  and  Ohio  grits :  for  first  and  second  stones ;  and 
Scotch  Water  of  Ayr,  Welsh,  and  Hindostan,  for  clearing-stones. 

The  grindstones  used  for  removing  surface  metal  are,  when  new,  from  5  to  7  feet  in  diameter, 
and  usually  run  at  a  speed  of  about  550  circumferential  feet  per  minute.  In  order  to  maintain  this 
speed,  notwithstanding  the  reduction  of  diameter  due  to  the  wear  of  the  stone,  the  pulley  attached 
to  the  shaft  upon  which  the  grindstone  is  hung  is  replaced  as  the  stone  wears  by  a  pulley  of  smaller 
diameter.  Grindstones  used  to  sharpen  instruments  usually  run  at  a  circumferential  velocity  varying 
from  about  180  to  350  feet  per  minute.  They  should  be  kept  very  true  by  being  turned"  up,  which 
operation  may  be  accomplished  by  using  a  piece  of  gas-pipe  as  a  turning  tool.  For  very  particular 
work  the  grindstone  requires  to  run  so  true  as  to  necessitate  the  use  of  the  black  diamond  or  bort  as 
a  turning  tool.  The  water  applied  to  a  grindstone  softens  it ;  hence  the  stone  should  not  run  in  a 
trough  of  water,  nor  be  allowed  to  stand  with  water  applied  to  any  part  of  it,  for  the  reason  that 
the  softer  parts  wear  away  the  quickest,  and  thus  throw  the  stone  out  of  true.  The  stone  should  be 
wetted  from  a  pipe  suspended  above  it,  and  provided  with  a  cock  to  shut  off  the  water  when  the 
stone  is  not  in  use. 

A  useful  device  for  truing  grindstones  is  shown  in  Fig.  2225.  It  consists  of  a  hardened  steel- 
threaded  roll  held  in  bearings  in  a  frame  or  stand,  which  is  bolted  to  the  grindstone  frame  in  such  a 
position  as  to  bring  the  thread  upon  the  roll  into  contact  with  the  face  of  the  stone.     The  action  is, 



that  the  tops  of  the  thread  crush  off  the  stone  in  minute  sections  or  granular  particles.  The  main 
stand  or  bottom  piece  is  securely  clamped  upon  the  trough  close  to  the  face  of  the  stone ;  then  by 
turning  the  hand- wheel,  the  threaded  roll  is  brought  iuto  contact  with  the  face  of  the  stone,  and  is 
allowed  to  remain  so  as  long  as  is  requisite  to  produce  the  desired  result.  The  water  is  to  be  left  as 
usual  in  the  trough.  When  by  long  use  the  thread  on  the  hardened  roll  becomes  worn,  it  can  be  re- 
cut,  which  operation  may  be  repeatedly  performed. 

In  grinding  tools  and  instruments,  a  cutting  edge  is  formed  by  the  line  of  junction  of  the  two 
f  acets°at  the  point  of  a  wedge.  The  angle  of  these  two  facets  one  to  the  other  is  determined  by  con- 
siderations of  strength,  and  the  shape  of  each  facet  either  by  considerations  of  strength  or  of  shape. 
As  a  rule,  the  harder  the  material  to  be  cut,  the  more  the  approach  of  the  two  facets  to  a  right 
angle,  one  with  the  other ;  and  so  likewise 
the  greater  the  strength  required,  the  nearer 
the  facets  to  a  right  angle.  Thus,  while  the 
facets  of  a  graver  may  stand  at  an  angle  of 
50°,  those  of  the  cutters  for  a  pair  of  shears 
or  a  punching  machine  will  stand  at  an  angle 
of  about  85°,  though  both  may  be  used  to 
cut  iron  and  steel.  In  this  latter  case,  the 
strength  being  the  main  consideration,  it  must 
be  obtained  at  a  sacrifice  of  keenness ;  where- 
as, if  we  take  the  case  of  a  razor  or  a  lance, 
sharpness  is  the  main  consideration,  and 
strength  is  disregarded. 

In  determining  upon  which  side  of  the 
stone  any  given  tool  should  be  ground,  the 
workman  takes  into  consideration  the  follow- 
ing points;  the  shape  of  the  tool,  the  amount 
of  metal  requiring  to  be  ground  off,  and  the 
condition  of  the  grindstone. 

Upon  the  edge  of  a  tool  which  last  receives  the  action  of  the  stone,  there  is  always  formed  what  is 
termed  a  feather-edge ;  that  is  to  say,  the  metal  at  the  edge  does  not  separate  from  the  body  of  the 
metal,  but  clings  thereto  in  the  form  of  a  fine  ragged  web.  If  now  we  take  a  point  on  the  circum- 
ference of  the  stone,  as  say  at  F,  Fig.  2226,  it  should  leave  contact  with  the  tool  at  the  point  of  the 
tool  denoted  by  D.  Instead  of  doing  this,  however,  the  metal  at  the  extreme  edge  gives  way  to  the 
pressure,  and  does  not  grind  off,  but  clings  to  the  tool,  leaving  a  web,  as  shown  from  D  to  E ; 
whereas,  if  the  same  tool  were  held  in  the  position  shown  at  0,  the  point  F  upon  the  stone  would 
meet  the  tool  at  the  edge  first,  and  would  cut  the  metal  clear  away  and  not  leave  a  feather-edge. 
Now  the  amount  of  the  feather-edge  will  be  greater  as  the  facets  forming  the  edge  stand  at  a  greater 
angle  one  to  another,  so  that,  were  the  facets  at  a  right  angle,  instead  of  forming  an  acute  wedge,  as 
shown  in  Fig.  2226,  the  feath- 
er-edge would  be  very  short  in- 
deed. But  in  all  cases  the  feath- 
er-edge is  greater  upon  soft  than 
upon  hard  metal,  and  is  also 
greater  in  proportion  as  the 
tool  is  pressed  more  firmly  to 
the  stone.  Therefore  the  work- 
man conforms  the  amount  of  the 
pressure  to  the  requirements,  by 
making  it  the  greatest  during 
the  early  grinding  stage,  when 
the  object  is  to  grind  away  the 
surplus  metal,  and  the  least 
during  the  latter  part  of  the 
process,  when  finishing  the  cut- 
ting edge ;  and  hence  he  obtains 
a  sharper  tool,  because  whatev- 
er feather-edge  there  may  be 
breaks  off  as  soon  as  the  tool  is 
placed  under  cutting  duty,  leav- 
ing a  flat  place  along  the  edge. 
The  main  principles  involved 
in  the  art  of  tool-grinding  may  be 
practically  applied  as  follows:  .  „. 

First,  to  define  the  point  which  distinguishes  whether  the  stone  is  running  to  or  from  you,  let  A,  ifig. 
2227,  represent  a  grindstone,  and  B,  C,  D,  E,  and  F  tools  held  thereon.  If  a  radial  line  from  the 
centre  of  the  stone'forms  an  obtuse  angle  with  the  face  of  the  tool  which  first  meets  a  point  on  the 
periphery,  or  face  of  the  stone  as  it  is  usually  termed,  then  the  stone  is  running  from  you ;  while 
if,  on  the  other  hand,  that  face  forms  an  acute  angle  to  the  radial  line,  then  the  stone  is  running 
to  you,  no  matter  in  what  position  in  regard  to  the  stone  you  may  stand.  In  ordinary  shop  par- 
lance, the  side  of  the  stone  on  which  the  face  of  the  stone  enters  the  trough  is  always  called  the  side 
with  the  stone  running  to  you,  because  all  grinding  which  requires  to  be  done  with  the  stone  running 
to  you  is  performed  on  that  side,  and  in  conjunction  with  the  use  of  the  rest  shown  in  Fig.  221,7.     It 



is  very  dangerous  to  grind  on  that  side  of  the  stone  without  using  the  rest  as  a  steadying  point  and 
as  a  safeguard.  B  and  C  are  ground  with  the  stone  running  from  you,  I)  is  neutral,  and  F  a.nd  F 
are  ground  with  the  stone  running  to  you.  Hence,  with  the  stone  running  to  you,  the  greater  the 
angle  of  the  front  face  of  the  tool  (that  is,  the  face  which  has  the  grindstone  running  toward  it),  the 

greater    the    liability 


of  the  tool  to  catch 
in  the  stone  and  the 
more  difficult  it  is  to 
hold  the  tool  steadily, 
while  the  reverse  is 
the  case  when  the 
stone  is  running  from 
you ;  and  it  follows 
that  as  the  length  of 
the  cutting-tool  edge 
is  greater,  the  more 
difficult  it  will  be  to 
hold  the  tool  in  thepo 
sition  of  J),  F,  or  /•'. 
Therefore  tools  having 
"  road  cutting  edges 
formed  by  acute  an 
glee  should  be  ground 
in  the  position  of  B, 
unless,  indeed,  the 
stone  is  very  true  and 

si >th,    and    has  no 

soft    spots,    in   which 

case  it  is  permissible  to  grind  them  held  in  a  position  relative  to  a  radial  line  of  the  stone  similar  to 
that  at  K ;  but  in  this  case  it  is  well,  while  holding  the  tool  at  that  angle,  to  grind  it  in  that  part  of 
the  circumference  of  the  stone  occupied  by  Df  or  between  that  and  the  position  occupied  by  J?,  so 
that,  should  ii  chance  to  catch  in  the  stone,  it  w  ill  not  drag  or  force  the  fingers  down  to  the  rest. 

We  may  now  consider  what  effect  the  size  of  the  work  has  upon  the  position,  relative  to  the  stone, 
in  which  it  should  be  ground,  by  giving  a  few  examples  of  grinding.  In  the  case  of  very  small 
articles  we  may  use  almost  any  part  of  a  true  stone,  because  the  hand  has  comparatively  a  thorough 
control  of  a  small  article.  To  grind  the  end  face  of  any  bar,  the  bar  is  always  placed  upon  the  rest, 
as  shown  in  Fig.  2227  at  F  ;  but  care  should  be  taken  to  move  the  bar  to  various  positions  along  the 
face  of  the  stone,  or  slowly  to  revolve  it,  causing  it  to  travel  across  that  face,  as  otherwise  a  groove 
will  be  worn  in  the  stone.  Any  work  requiring  to  be  ground  to  a  point  must  be  held  in  the  position 
shown  at  //,  Fig.  2226;  it  should  lie  moved  across  the  face  of  the  stone  as  the  grinding  proceeds, 
to  prevent  the  wearing  of  a  groove  in  the  stone.  The  Burface  of  sheet-metal  or  plates  slnuld  be 
ground  in  the  position  occupied  by  /<*,  Fig.  2227.  The  cutting  edges  id'  all  blades  should  be  ground 
in  the  position  Bhown  at  G  <>r  //  in  Fig.  2226,  because  they  can  be  held  steady,  and,  if  held  lightly 
toward  the  finish,  with  a  small  amount  only  of  feather-edge.  All  drills  should  be  ground  upon  the 
ends  while  upon  the  rest,  excepting  the  faces  of  flat  drills,  as  at  //,  while  the  diametral  edges  must 
be  ground  as  at  F,  Fig.  2227.  Anything  that  is  sufficiently  long  to  afford  a  firm  grip  with  both 
hands  when  standing  in  the  position  of  /''may  be  ground  in  that  position,  providing  that  the  top  of 
the  rest  is  close  to  the  perimeter  of  the  stone.  All  blades  requiring  a  keen  edge  must  be  held  lightly 
to  the  stone,  to  avoid  getting  broad  and  thick  feather-edges. 

After  a  tool  is  ground,  it  is  often  necessary  to  remove  the  feather-edge  without  having  recourse  to 
an  oilstone.  Machinists  often  accomplish  this  object  by  drawing  the  cutting  edge  across  a  piece  of 
wood,  holding  the  cutting  edge  parallel  with  the  line  of  motion,  which  removes  the  feather-edge  w  ii  li- 
mit breaking  it  off  low  down,  as  would  be  the  case  if  the  length  of  the  cutting  edge  stood  at  a  right 
angle  to  the  line  of  motion. 

Power  required  to  drive  Grindstones. — According  to  Ilartig's  experiments,  to  drive  grindstones 
empty,  the  power  is  expressed  by  the  following  foimulas: 

Large  grindstones  emptv,  P=  .0000409  d  v,  or  P=  .000128  d"1  n. 

Small  fine  grindstones  empty,  P  =  0.16  +  .0000895  d  v,  or  P—  0.16  +  00028  J2  n. 

In  these  formulas  P=  power  required,  d  =  diameter  of  stone  in  inches,  v 
minute,  and  n  =  number  of  revolutions  per  minute. 

The  coefficients  of  friction  between  grindstones  and  metals  are  as  follows  : 

velocity  in  feet  per 

Coarse  grindstones  Fine  grindstones 

at  high  speeds.  at  low  speeds. 

For  cast-iron 22  .72 

"    wrought-iron 44  1.00 

"   steel 29  0.94 

Grindstone's  net  work;  P  — 

P  Kv 

In  this  formula  P  =  pressure  between  material  and  stone,  v  =  circumferential  velocity  of  stone  in 
feet  per  minute,  and  K  =  the  coefficient  of  friction.  J.  R.  (in  part.) 


GUN",     See  Air-Gcn,  Fire-Ahms,  and  Ordnance. 

GUN-CARRIAGE.     See  Ordnance. 

GUN-COTTON.     See  Explosives. 

GUNPOWDER.     See  Explosives. 

GUTTA-PERCHA.  A  gum  obtained  from  the  Isonandra  gutta,  a  tree  indigenous  to  the  Malay 
Archipelago.  Its  density  is  a  little  above  that  of  water.  At  ordinary  temperature  it  is  supple,  very 
tenacious,  extensible,  but  not  very  elastic.  At  112°  F.  it  softens,  and  at  212°  it  becomes  adhesive 
and  pasty,  so  that  it  may  be  moulded  into  any  desired  form.  On  cooling  it  becomes  hard  and  firm. 
It  may  thus  be  used  for  taking  impressions  of  objects  or  for  making  moulds  for  electrotypers,  as  it 
preserves  even  the  finest  lines  and  markings.  At  266°  gutta-percha  melts.  At  higher  heats  it  boils 
and  undergoes  partial  distillation,  yielding  a  light  solid  residue  and  oils  formed  chiefly  of  isoprene 
and  caoutchoucene.  Normally  of  cellular  texture,  under  strong  traction  it  becomes  fibrous  and  much 
more  resistant.  Thus,  when  by  a  powerful  pull  its  length  is  doubled,  it  supports  without  breaking 
the  strain  of  a  force  double  that  required  to  produce  its  extension.  This  resistance  is  not  offered  in 
all  directions,  as  the  material  when  thus  extended  is  easily  torn  by  transverse  strain. 

Gutta-percha  is  a  bad  conductor  of  heat,  but  the  best  insulating  substance  for  electricity  known. 
It  welds  easily,  simple  warming  of  the  pieces  being  all  that  is  required.  It  is  insoluble  in  water  at 
all  temperatures,  and  withstands  steam  well.  It  resists  the  action  of  acids  and  alkalies  better  than 
India-rubber,  and  is  unattacked  by  the  most  powerful  of  chemical  reagents,  hydrofluoric  acid.  It  is 
soluble  in  alcohols  and  turpentine,  and  cissolves  best  in  benzine,  chloroform,  and  bisulphide  of  car- 
bon. These  agents  do  not  cause  it  to  swell  as  they  do  India-rubber,  but  gradually  dissolve  it  from 
the  surface  to  the  interior.  The  solution  becomes  colorless  on  filtration,  and  if  evaporated  leaves 
gutta-percha  in  a  pure  state,  when  it  resembles  wax. 

When  exposed  to  air  and  light,  pure  gutta-percha  becomes  rapidly  modified,  disengaging  a  peculiar 
acid  odor.  The  surface  hardens  and  splits  in  all  directions.  Thus  modified,  the  material  loses  most 
of  its  valuable  qualities ;  it  becomes  even  an  electrical  conductor,  and  is  transformed  into  a  kind  of 
friable  resin  insoluble  in  benzine.  Much  of  this  resinous  substance  is  found  in  commercial  gutta- 
percha, owing  to  the  exposure  of  the  material.  The  alteration  is  best  prevented  by  immersion  of  the 
substance  in  water  in  a  dark  place. 

The  following  are  some  of  the  principal  characteristics  in  which  gutta-percha  and  India-rubber 

Gutta-percha,  when  immersed  in  boiling  water,  contracts  in  bulk,  while  India-rubber  expands  and 
increases  in  bulk. 

Gutta-percha  juice  is  of  a  dark-brown  color,  and  consolidates  in  a  few  minutes  after  exuding  from 
the  tree,  when  it  becomes  about  as  hard  as  wood.  India-rubber  sap  is  perfectly  white,  and  of  about 
the  consistence  of  thick  cream  ;  when  it  coagulates  it  gives  from  4  to  6  parts  of  water  out  of  10 ;  it 
may  be  kept  like  milk,  and  is  frequently  drunk  by  the  natives. 

Gutta-percha,  first  treated  with  water  alcohol,  and  ether,  and  then  dissolved  in  spirits  of  turpen- 
tine and  precipitated,  yields  a  substance  consistent  with  the  common  properties  of  gutta-percha. 
Similar  treatment  of  India-rubber  results  in  a  substance  resembling  in  appearance  gum  arabic. 

Gutta-percha  by  distillation  yields  57f  per  cent,  of  volatile  matter,  while  India-rubber  yields  85f 
per  cent. 

Gutta-percha  in  its  crude  state,  or  in  combination  with  other  materials,  may  be  heated  and  reheated 
to  the  consistence  of  thin  paste,  without  injury  to  its  future  manufacture.  India-rubber,  if  but  once 
treated  in  the  same  manner,  will  be  destroyed  and  unfit  for  future  use. 

Gutta-percha  is  not  decomposed  by  fatty  substances ;  one  application  of  it  is  for  oil-vessels.  In- 
dia-rubber is  soon  decomposed  by  coming  in  contact  with  fatty  substances. 

Gutta-percha  is  a  non-conductor  of  cold,  heat,  and  electricity,  and  in  its  natural  state  is  non-elastic, 
and  with  little  or  no  flexibility.  India-rubber  is  a  conductor  of  heat,  cold,  and  electricity,  and  is 
highly  elastic  and  flexible. 

The  specific  gravity  of  gutta-percha  is  much  less  than  that  of  India-rubber — in  the  proportion  of 
100  of  gutta-percha  to  150  of  India-rubber. 

Preparation. — The  preparation  of  gutta  percha  does  not  materially  differ  from  that  of  India-rub- 
ber. (See  India-Rubber.)  The  crude  material  is  delivered  to  commerce  in  blocks  weighing  from  2 
to  5  lbs.  each,  filled  with  impurities.  In  order  to  purify  it,  the  blocks  are  cut  into  slices  by  the 
machine  represented  in  Figs.  2228  to  2230.  Fig.  2228  is  a  side  elevation,  Fig.  2229  a  front  eleva- 
tion, and  Fig.  2230  a  sectional  view.  A  A  represents  the  framework.  B  is  a  circular  iron  plate, 
of  about  5  feet  diameter,  in  which  are  three  slots,  into  which  are  inserted  three  radial  knives,  in  a 
similar  manner  to  the  irons  of  an  ordinary  plane  or  spoke-shave.  B*  is  a  shaft,  to  the  end  of  which 
the  plate  B  is  attached,  and  by  means  of  which  it  is  made  to  revolve  at  any  desired  velocity,  motion 
being  communicated  to  the  shaft  from  a  steam-engine,  or  any  other  convenient  first  mover,  through 
the  medium  of  gearing  or  drums.  D  is  an  inclined  shoot,  down  which  the  lumps  of  crude  gutta- 
percha are  dropped  against  the  knives  of  the  revolving  plane  B,  by  which  they  are  cut  into  slices  of 
a  thickness  corresponding  to  the  degree  of  projection  given  to  the  knives.  The  speed  of  this  machine 
is  about  200  turns  per  minute.  The  slices  are  afterward  collected,  and  put  into  a  vessel  tilled  with 
hot  water,  where  they  are  left  to  soak  till  they  feel  soft  and  pliable  to  the  touch,  and  until  all  the 
leaves  and  other  impurities  contained  in  the  mass  are  separated  from  it.  In  this  partially  purified 
state  the  material  is  taken  to  a  carder,  or  large  circular  box  containing  a  cylinder  or  drum  covered 
with  curved  teeth.  This  runs  at  a  speed  of  about  800  turns  per  minute,  and  shreds  the  gutta-percha 
into  small  pieces,  which  fall  into  a  vat  of  water  placed  below.  The  gum  being  porous  floats  on  the 
surface,  and  the  impurities  are  precipitated. 

Another  machine  for  this  purpose  is  represented  in  Fig.  2231,  which  subjects  the  gutta-percha  to 
a  very  thorough  working  over.     The  crude  gum  is  presented  by  the  feeding  rollers  G[  to  the  action 



of  the  first  breaker  F\  It  is  by  the  latter  broken  up  into  shreds  or  fragments,  and  considerable 
quantities  of  earthy  and  other  extraneous  matters  arc  beaten  out  of  and  disengaged  from  it,  the 
whole  falling  in  a  mingled  mass  into  the  water  contained  in  the  compartment  f  of  the  tank,  where  the 
different  materials  assort  themselves  according  to  their  specific  gravities.     Such  pieces  as  consist  of 



pure  gutta-percha,  or  in  which  gutta-percha  predominates,  float  on  the  Burface  of  the  water,  while 
most  of  the  earthy  and  other  extraneous  matters  sink  to  the  bottom.  The  revolving  endless  web  Ha 
then  draws  toward  it  the  floating  gutta-percha,  and  carries  it  upward  to  the  Becondsetof  feeding- 
rollers  (<"\  mounted  over  the  Becond  compartmenl  /'  of  the  tank,  from  which  rollers  it  is  delivered  to 
the  Becond  breaker  /'"•',  to  undergo  a  repetition  of  the  process  which  has  been  just  described,  in  order 
to  its  being  further  disentangled  and  purified.  From  the  Burface  of  the  water  in  the  compartment 
f  the  gutta-percha  is  carried  up  the  inclined  endless  web  //:1  to  the  rollers  (,''■',  which  deliver  it  to 
the  third  breaker  F*  over  the  compartmenl  r*,  bj  which  it  is  a  third  time  broken  up,  in  order  to 
separate  any  remaining  impurities  from  it.  The  inclined  endless  wt  b  // '  uexl  cai ries  it  forward  to 
the  rollers  iv4,  which  present  it  to  the  revolving  cylinder  A',  by  the  blades  of  which  it  is  cut  or 
minced  into  a  multitude  of  very  thin  Blivers,  which,  as  thej  fall  into  the  water  in  /•'',  are  thrown  for- 
ward in  the  direction  of  the  agitator  .'/.  A-  this  agitator  revolves  in  a  direction  opposite  to  that  in 
which  the  Boating  mass  of  gutta-percha  is  moving,  it  forces  the  gutta-percha  down 

into   the  Water,  and    to   take  a  circuitous   course  through    it    toward   the   lame  endless 

web  A',  whereby  it  is  washed  free  from  any  dirt  which  may  have  collected  upon  it  in 
passing  through  the  preceding  operations.  By  the  endless  web  N  the  gutta-percha 
is  next  moved  onward  to  the  scries  of  rollers  /.'/,',  8  8  .■  and  from  the  last  pair  of 

the  scries  the  gutta-percha  is  raised  by  an  endless  revolving  web  O  to  a  pair  of  metal 


Y     T 



'"■'■'"       --:■■—-: '  '-  - 

pressing  and  finishing  rollers  }'!  F9,  which  are  set  by  adjusting  screws  to  a  distance  from  one  an- 
other equal  to  the  thickness  of  the  sheet  or  hand  into  which  it  is  now  desired  that  the  gutta-percha 
should  l)i>  compressed.  After  passing  through  between  F1  and  1"-',  the  sheet  or  baud  is  carried 
back  over  the  topmost  of  those  rollers,  I"5,  and  then  over  the  wooden  drum  U,  to  be  wound  on  a 
taking-up  roller  v.    In  cast' it  is  desired  to  unite  the  gutta-percha  with  cloth,  for  the  manufacture 

of  a  water-proof  fabric,  the  cloth  is  led  in  as  shown  at  II',  ami  is  firmly  united  to  the  pun  by  pres- 
sure between  the  roller  )"•'  and  drum  /'.  Alter  passing  through  the  carder  previously  described,  the 
gutta-percha  is  kneaded  and  rolled  into  sheets. 

In  order  to  cut  the  sheet  gum  into  strips  or  bands  of  any  shape,  an  ingenious  machine  devised  by 

Charles  Hancock  in  1844  is  used.     It  consists  simply  of  two  steel  rolls  grooved  on  their  surface. 

The  grooves  on  each  roll  are  semicircular,  so  that  when  the  rolls  are  superposed  a  scries  of  cylindri- 
cal orifices  is  formed  between  them.  The  material,  previously  heated,  is  passed  between  the  rolls, 
which  cut  it  into  cylindrical  strips,  or  strips  of  an\  desired  shape  of  section,  corresponding  with  the 
form  of  the  grooves.  Another  method  of  cutting  sheets  into  Strips  is  by  the  use  of  a  large  number 
of  parallel  blades  mounted  on  a  single  moving  support. 

The  form  of  calenders  used  in  the  manufacture  of  sheet  gutta-percha  is  represented  in  Figs,  2232 
and  2288.  The  rolls  are  6  feet  -1  inches  long  and  '2"2  inches  in  diameter,  each  one  weighing  about 
7,000  lbs.      They  are  heated  by  steam. 

Gutta-percha  tubes  arc  made  by  forcing  the  gum  over  a  steel  mandrel  held  as  a  core  in  a  cylinder 
of  iron.  As  the  material  is  hot  on  emerging,  the  sides  of  the  tube  would  naturally  stick  together. 
To  prevent  this,  the  tube  as  fast  as  it  is  formed  is  led  through  a  vat  of  water  some  50  feet  in  length. 



The  water,  pressing  equally  on  the  interior  as  well  as  the  exterior  of  the  tube,  keeps  it  in  shape  until 
it  cools  and  sets.     By  this  means  a  single  tube  of  nearly  1,100  feet  in  length  has  been  made  without 

a  break  of  any  kind. 


An  important  utilization  of  gutta-percha  is  as  an  insulating  material  for  electrical  conducting, 
wires.  A  thin  coating  of  the  gum  may  be  applied  to  a  wire  by  passing  the  latter  through  a  vessel 
containing  the  gutta-percha  in  a  melted  state.  This  method,  however,  does  not  answer  for  applying 
the  gutta-percha  envelope  to  sub- 
marine or  subterranean  cables. 
For  this  purpose  the  gum  is  puri- 
fied with  the  greatest  care,  and 
is  placed  in  a  cylinder,  where  it 
is  kept  plastic  by  heat,  and  at 
the  same  time  is  strongly  com- 
pressed by  a  piston.  The  wires 
composing  the  core  of  the  cable 
are  caused  to  pass  through  a 
chamber  into  which  the  gum  also 
enters,  and  at  the  same  time  are 
rotated,  so  that  they  emerge  cov- 
ered with  a  layer  of  gutta-percha, 
which  is  increased  in  thickness  as 
desired  by  repetitions  of  the  pro- 

"Vulcanization  of  gutta-percha 
is  effected  in  the  same  manner  as 
that  of  India-rubber.  The  opera- 
tion renders  the  material  much 
harder,  but  it  is  not  nearly  so 
necessary  to  adapt  it  to  various 
purposes  as  in  the  case  of  caout- 
chouc ;  hence  it  is  not  often  done. 
The  impossibility  of  working  or 
dissolving  gutta-percha  or  rub- 
ber after  vulcanization  has  led 
to  many  attempts  to  remove  the 
sulphur,  the  most  successful  of 
which  is  noted  under  India-Rub- 
ber. In  vulcanizing  gutta-percha, 
when  the  proportion  of  sulphur 

is  increased  and  the  heat  prolonged,  a  very  hard  black  substance  is  produced,  which  is  susceptible 
of  high  polish,  and  which  may  be  worked  like  ivory.  This  is  commonly  made  into  combs  and  various 
objects  of  art.     Gutta-percha" is  largely  used  by  dentists  as  a  foundation  for  artificial  dentures. 


Works  for  Reference. — See  articles  "  Gutta-Percha  "  in  Ure's  "  Dictionary  of  Arts  and  Manufac- 
tures," and  in  the  "American  Cyclopaedia."     See  also  Figuier's  "  Merveillee  de  PIndustrie  " 

GYROSCOPE.*  A  name  applied  to  various  instruments  designed  to  illustrate  the  phenomena  of 
rotation.  The  most  curious  and  generally  interesting  form  of  gyroscope,  rightly  named  "  mechanical 
paradox,"  Fig.  2234,  although  its  principle  was  discovered  long  before  its  first  construction,  consists 
essentially  of  a  disk  revolving  on  pivots  within  a  ring,  having  on  the  line  of  prolongation  of  its  axis, 
on  one  side,  a  bar  or  spur  with  a  smooth  notch  beneath  to  receive  the  hard  smooth  point  of  an  up- 
right support.     Thus  placed,  when  the  disk  is  not  turning,  the  whole  falls,  of  course,  like  any  heavy 

body  unsupported.     Rotate  rapidly  by  unwind- 
2234  ing  a  string,  set  on  the  support,  but  uphold  the 

..^s»-*" " opposite  side  of  the  ring;  no  peculiar  move- 

_-•-"'  '""■  ^  ment  then  occurs.    But  if  while  the  disk  is  rap- 

^k   ^\^  idly  turning,  the  bar  being  on  the  support,  the 

flQv|  opposite  side  be  set  free,  the  whole,  instead  of 

^s5*5™™  W^^s.   \      falling,  as  would    be   expected,  commences    a 

s^-fc       (HI  Ij      Jjv^.     steady  revolution  in  a  horizontal  circuit  about 

^T\~"""  Jp->     the  point  of  support,  moving  more  rapidly  as 

^v~~~— ~J '  «I  IL^-"'  tni'  primaiy  rotation  is  expended,  and  sinking, 

~~~Vf  »  at  first  imperceptibly,  then  more  rapidly,  until 

>*'  in  from  one  to  three  minutes  it  comes  to  rest. 

^^   |    ^  Mathematical  analysis  shows  that  when  set  free 

/  '<   - X  -S  it  continually  falls  and  rises,  but  this  motion  is 

//  ((QHw).      \  '  "",  visible.     The  disk  started  with  its  axis  in 

I   V^Ss^BEjrl,.  or   below   the    horizontal   never  rises,  without 

\  ^z^iLf.^t&jr  aid,  above  it-  first  position.     Started  with  high 

""^wliin^^^  speed  above  the  horizontal,  it  may  rise;  and  if 

its  connection  with  the  support  allow,  as  when 
this  is  by  a  ball  and  socket,  it  may  even  ascend  to  a  vertical  position,  and  spin  as  a  top.  Arrested  in 
its  traveling  movement,  it  always  descends ;  hastened,  it  rises.  Checked  in  any  part,  it  inclines  in  the 
direction  of  that  part.  In  the  form  now  given,  the  traveling  or  orbital  movement  is  always  in  the 
direction  in  which  the  bottom  "f  the  disk  is  going.  But  it  the  axis  be  prolonged  beyond  the  support, 
and  the  disk  and  ring  Blightly  overpoised  by  a  weight  on  the  other  side,  then  the  disk  always  travels 
in  the  direction  in  which  its  top  is  going,  and  nearly  all  the  phenomena  are  reversed.  Many  other 
curious  results  may  be  obtained  ;  it  will  here  be  added  further  only  that  the  disk  below  the  horizon- 
tal is  always,  and  above  it  usually,  slowly  falling;  and  that  the  orbital  motion  invariably  takes 
place  toward  that  side  of  the  disk  in  which  the  force  of  the  rotation  about  its  own  axis  is  most  re- 
sisted  or  checked.  For  proof  of  this  latter  principle,  let  any  small  wheel  be  rotated,  and  while  turn- 
ing rub  or  seize  it  upon  any  side;  the  rotation  in  this  side  being  thus  checked,  and  actually  or  in 
effect  subtracted  from,  that  in  the  opposite  side  preponderates,  and  the  wheel  is  urged  toward  the 
side  in  which  the  checking  occurs. 

Perhaps  no  completely  satisfactory  explanation  of  the  phenomena  can  be  given  without  employing 
the  language  and  processes  of  the  higher  mathematics.  This  has  been  clone  in  a  very  complete 
manner  by  Gen.  J.  G.  Barnard  in  a  paper  published  in  the  "American  Journal  of  Education"  for 
June,  1857,  and  also  published  separately  under  the  title  "Analysis  of  Rotary  Motion  as  applied  to 
the  Gyroscope "  (New  York,  1857).  The  following  explanation,  proposed  by  Dr  Levi  Reuben  of 
New  York,  is  perhaps  as  satisfactory  as  it  is  possible  to  give  without  the  aid  of  mathematics.  There 
are  two  facts  to  be  explained:  support,  and  orbital  movement,  or  traveling  about  the  supporting 
point.  For  the  first,  suppose  the  disk  composed  of  1,000  equally  heavy  particles.  'When  it  is  set 
rotating  and  released,  each  of  these  particles  is,  as  a  separate  ball,  acted  on  by  two  moving  forces, 
that  giving  the  rotation,  and  that  of  gravity  ;  but  the  whole  is  also  held  together  by  the  constrain- 
ing action  of  cohesion.  Suppose  that,  when  released,  the  axis  points  below  the  horizontal  .  gravity 
acts  in  vertical  lines  and  equally  on  all  the  particles.  Its  direction  and  amount  may  be  represented 
by  equal  short  pendent  threads  dropping  down  from  all  the  particles.  If  the  particles  be  also  sup- 
posed in  a  single  plane,  the  extremities  will  all  lie  in  a  new  plane,  slightly  without  and  below  the 
plane  of  the  disk,  and  parallel  with  it.  The  forces  impressed  in  giving  rotation  upon  the  several 
particles  of  the  disk  will  all  point  in  its  plane,  being  represented  at  any  moment  by  tangents  to  the 
circles  in  which  the  several  particles  move,  pointing  in  all  directions,  and  varying  in  length  from  the 
axis,  where  this  is  zero,  to  the  periphery,  where  it  is  a  maximuim  But  the  resultant  movements  or 
tendencies  of  the  particles  must  all  terminate  in  the  exact  plane  in  which  the  gravitative  components 
were  seen  to  terminate.  Every  particle  thus  acted  upon,  then,  tends  to  go  outward  or  forward  into 
the  new  plane  already  referred  to.  The  several  pressures  are  to  points  scattered  somewhat  widely 
in  that  plane  ;  but  owing  to  the  cohesion  of  all  the  particles,  they  are  constrained  to  move  or  press 
forward  in  a  body.  The  effect  is  as  if  the  whole  disk  were  pulled  outward  and  very  slightly  down- 
ward, while  the  pivot  in  the  notch  reacts  or  pulls  in  the  opposite  direction  ;  and  the  wheel  is  sup- 
ported, in  part,  as  if  slung  up  by  strings  attached  to  its  two  faces  and  pulled  in  opposite  directions. 
When  the  disk  is  above  the  horizontal,  the  new  plane  is  behind  or  within  it ;  it  then  pushes  against 
the  pivot,  and,  this  reacting,  there  occurs  support  by  opposite  pressures,  instead  of  tractions.  Thus 
we  discover  one  reason  why  no  material  support  is  needed  for  the  remote  end  of  the  axis  ;  while  as 
a  consequence  of  this  view,  if  the  axis  be  horizontal  it  must  first  sink  slightly,  yet  it  may  be  only  im- 
perceptibly, before  support  can  occur.  This  agrees  entirely  with  the  results  of  mathematical  analysis. 
In  the  second  place,  why  does  the  disk  travel  around  the  supporting  point  ?     When  not  overpoised, 

*  From  the  "  American  Cyclopa-dia  " 




gravitation  acting  downward,  and  rotation,  in  the  ascending  side  of  the  disk,  upward,  the  latter  is  in 
effect  decomposed  into  a  horizontal  and  a  vertical  component,  the  horizontal  expressing  itself  in  the 
pressure  already  referred  to,  the  vertical  being  resisted  or  antagonized  by  the  force  of  gravity  ;  the 
result  for  each  particle  being  the  sum  which  the  latter  as  a  negative  quantity  would  form  with  the 
former.  In  the  ascending  side,  therefore,  gravity  overbalances,  equals,  or  diminishes,  according  to 
the  place  of  each  particle,  the  rotative  force  of  ascent  acting  upon  it ;  but  to  the  vertical  component 
of  the  rotative  force  of  all  the  particles  in  the  descending  side  it  adds  alike  a  quantity  of  action 
equal  to  its  own  amount.  Hence,  the  whole  rotative  force  in  the  descending  half  may  be  considered 
as  increased,  that  in  the  ascending  as  diminished.  There  will  be  some  point  in  the  ascending  half  at 
which  the  vertical  component  of  rotation  equals  gravity ;  this  will  become  in  effect  a  point  of  rest, 
or  of  no  action.  This  is  then  the  point  pierced  by  the  resultant  axis — the  point  about  which  all  the 
particles  under  the  combined  forces  will  tend  to  revolve :  those  in  the  ascending  half  starting  with 
less  radii  to  sweep  around  this  point  as  a  centre ;  those  in  the  descending  starting  with  longer  radii, 
and  sweeping  in  longer  curves  about  the  same  point.  Thus  the  disk  is  continually  carried  to  the 
side  in  which  the  action  is  most  checked ;  and  this  constitutes  the  traveling  movement.  _  When  over- 
poised on  the  opposite  side,  the  action  of  gravity  on  the  disk  itself  is  upward,  the  axis  acting  asa 
lever  the  support  on  which  it  rests  as  a  fulcrum :  the  rotative  force  of  the  descending  particles  is 
now  resisted  by  it ;  and  for  a  like  reason  the  disk  now  moves  toward  its  descending  side.  When  not 
overpoised,  the  traveling  movement  of  the  disk  itself  introduces  a  new  element  into  the  case,  by  re- 
sisting the  rotating  of  particles  in  the  upper  half  backward  in  the  course  of  movement.  This  checks 
and  diminishes  the  action  in  the  upper  half  of  the  disk,  and  constitutes  a  new  source  of  support  by 
generating  a  tendency  upward ;  and  it  is  doubtless  this  part  of  the  action  that  raises  the  disk  at 
times  to  an  erect  position.  The  principles  thus  arrived  at  explain  also  why  the  disk  travels  faster 
as  its  axial  rotation  lessens,  and  also  when  weights  are  added  to  it ;  why  in  the  ordinary  form  it 
rises  if  its  motion  is  hastened  with  the  hand;  why,  if  overpoised,  it  descends  by  being  hastened,  and 
rises  on  being  delayed  in  its  orbital  movement ;  and  in  fact,  it  may  safely  be  said,  every  phenomenon 
which  the  instrument  can  be  made  to  present.  The  same  explanation,  in  effect,  applies  if  the  rotat- 
ing body  be  a  sphere,  or  of  any  other  form 

The  facts  of  support  and  orbital  movement,  though  separately  considered,  are  really  but  two  dif- 
ferent expressions  of  the  same  phenomenon ;  the  two  actions,  here  for  convenience  separated,  really 
conspire  in  one  movement,  and  that  is  the  composition  of  a  rotation  caused  by  gravity  with  an- 
other imparted  by  the  hand.  The  reason  why  the  rotating  body  does  not  fall  is  that,  in  such  a 
body,  whenever  its  plane  is  oblique  to  the  vertical,  gravity  is  no  longer  allowed  to  act  singly, 
but  "must  in  every  instant  enter  into  composition  with  an- 
other force.  Hence  the  body  in  such  case  cannot  simply 
fall,  but  must  move  toward  such  new  place  in  space  as  the 
combined  actions  shall  determine ;  and  hence,  again,  the 
same  force  which  ordinarily  produces  a  vertical  fall,  here 
carries  a  body  round  in  a  horizontal  circle,  or  secondarily 
sometimes  even  causes  it  to  ascend.  The  weight  of  the  ro- 
tating disk,  however,  is  in  all  positions  sustained  by  the 
support  and  base  on  which  the  apparatus  rests.  In  this  ex- 
planation, the  distance  through  which  the  gravitative  force 
acts  has  been  taken  as  very  short,  because  by  experiment 
and  calculation  it  can  be  proved  that,  unless  the  weight  of 
the  ring  is  very  great,  the  whole  downward  action  of  grav- 
ity on  the  disk  is  very  slight  compared  with  that  of  the  ro- 
tation first  imparted  by  the  hand,  sometimes  as  small  as  in 
the  ratio  of  1  to  40  or  60. 

HACKLE.     See  Flax  Machinery. 

HAMMERS,  HAND.  The  nature  of  work  to  be  done  by 
hammers  calls  for  very  great  differences,  not  only  in  the 
form,  material,  and  weight  of  the  hammer-head,  but  also  in 
the  appendages  to  it.  There  are  the  material  and  form  of 
the  handle,  the  angle  at  which  the  handle  should  intersect 
the  axial  line  of  the  hammer-head,  the  position  of  the  cen- 
tre of  gravity  with  respect  to  the  intersection  of  this  axial 
line,  and  the  length  and  elasticity  of  the  handle.  If  the 
centre  of  gravity  is  not  in  the  central  line  or  longitudinal 
axis  of  the  hammer-head,  then  there  is  a  tendency  to  bring 
the  hammer  down  on  the  edge  of  the  face,  and  not  on  the 
face.  If  this  defective  construction  be  great,  the  muscles 
of  the  wrist  may  not  be  strong  enough  to  counteract  the 
tendency.  If  the  defective  construction  be  slight,  then  the 
work  is  often  marked  with  angular  indents.  Arrangements 
too  may  be  required  for  modifying  the  intensity  of  the  blow 
while  retaining  the  effects  resulting  from  a  heavy  hammer, 
where  a  light  one  would  be  inefficient. 

In  dealing  with  hammers  the  following  questions  claim 
careful  consideration :  What  power  or  energy  is  in  a  hammer  of  known  weight  moving  at  a  known 
velocity,  if  brought  to  a  state  of  rest  by  impact  on  a  block  ?  Can  this  impact  effect  of.  a  hammer 
be  converted  into  simple  pressure,  and  be  stated  as  a  load  or  weight  placed  where  the  impact  is 
requisite  to  produce  the  same  effect  as  the  impact  did  ?     If  the  mode  of  solving  the  first  question 



be  made  clear,  then  the  answer  to  the  second  can  be  readily  obtained.  The  measurable  elements 
which  affect  the  result  are  a  variation  in  the  mass  of  the  hammer-head  and  a  variation  in  the  length 
of  the  handle.  By  a  varied  mass  there  is  a  varied  weight  in  the  hammer ;  by  a  varied  length  of 
handle  there  will,  with  the  same  muscular  effort,  be  a  varied  velocity  in  this  mass ;  and  upon  a  com- 
bination of  mass  and  velocity  depends  the  produced  energy.  (See  Dynamics.)  Now,  if  a  mass  of 
metal  moving  at  a  known  velocity  strike  an  object,  the  energy  of  the  blow  results  from  the  condi- 
tions at  the  moment  of  impact.  For  example,  the  work  done  in  the  hammer  H,  Fig.  2235,  as  it 
strikes  the  nail  N,  does  not  depend  upon  its  velocity  through  the  arc  Q  iV,  but  only  upon  its  velocity 
when  commencing  contact  with  the  nail.  Hence,  60  long  as  the  material  which  gives  the  blow  and 
the  mass  of  it  are  the  same,  it  is  not  of  any  consequence  how  the  velocity  was  accumulated.  It  may 
result  from  centrifugal  or  rectilinear  action,  or  from  muscular  effort,  steam-pressure,  or  gravity. 
Hence,  other  elements  remaining  unchanged,  whatever  accelerates  the  velocity  of  a  hammer  increases, 
according  to  very  clear  rules,  the  energy  of  that  hammer. 

Custom  and  certain  mathematical  considerations  have  led  to  the  adoption  of  the  height  of  the  fall 
needful  to  impart  a  velocity,  rather  than  the  velocity  itself,  as  the  element  to  be  combined  with  the 
mass  of  a  hammer  in  order  to  determine  its  actual  energy.  It  may  therefore  be  stated  that  the 
simple  pile-driving  machine  or  drop-hammer,  in  which  the  head  falls  under  the  action  of  gravity 
only,  is  the  representative  form  into  which  all  hammers  must  be  converted  in  order  to  calculate  en- 
ergy. The  laws  governing  falling  bodies,  explained  fully  under  Dynamics,  will  make  clear  the  prin- 
ciples governing  the  present  ease.  To  estimate  the  work  in  the  blow  of  the  hammer,  the  space 
through  which  the  hammer-head  must  fall  under  the  influence  of  gravity,  in  order  to  acquire  the 
velocity  of  impact,  must  be  determined.  Then,  if  this  deduced  space  be  combined  with  the  weight 
in  pounds  of  the  hammer,  we  shall  have  the  measure  of  the  energy  of  the  latter. 

Example. — Suppose  a  hammer-head  weighs  2  lbs.,  and  the  velocity  at  the  instant  of  the  blow  was 
observed  to  be  at  the  rate  of  25  feet  per  second  :  then  the  space  through  which  under  the  influence 

T-         (•|r>)2  625 

of  gravity  it  must  have  fallen  to  acquire  this  velocity  will  be  s=        =  —         —  = —  9.7  feet, 

2  g       2  x  32.2       64.4 

or  10  feet  nearly.  Then  the  work  of  one  blow  of  that  hammer  would  be  represented  by  2  x  10  =  20 
foot-pounds ;  that  is  to  say,  the  blow  of  this  two-pound  hammer  would  produce  an  effect  similar  to 
that  of  a  weight  of  20  lbs.  falling  through  a  space  of  1  foot,  or  40  lbs.  through  60  inches,  or  240 
lbs.  through  1  inch.  The  following  table,  by  Major  Maitland  of  the  Royal  Gun  Factories,  Woolwich, 
England,  gives  a  number  of  valuable  experiments  and  calculations  relative  to  hammers.  They  were 
made  upon  copper  cylinders,  and  the  mean  from  three  experiments  of  the  compression  of  each  from 
one  blow  of  the  hammer,  described  in  the  first  and  second  columns,  is  stated  in  the  third ;  the  other 
columns  in  the  table  explain  themselves  : 

Table  Shotting  Force  of  Hamnu  rs. 




-   -B     O     L 






35    : 

C    ■» 

liirh  with. mi 
!  been  place. 
Cylinders    t 
ective  Com 
mn  3. 

















►   tf 

«  s 

.£    S  °   :   g 

■o   -^    ®    1;    c 








•3  felfl 
s  .=  S  ft  s. 













a,  .145) 






&,  .166  V 



(say)  96 







o,  .158  \ 


(I,  .8-31 

Light  sledge  (raised). . . 

"  1 

<?,  .329  )■ 
/,  .314  J 
(h  .325  ) 





7'  8, 1 




Light  sledge  (swung)  . . 

h,  .333  V 










i.  .34s  \ 


3,  .374  ) 

Heavy  sledge  (raised).. 


%,  .876  y 

I,  .371  j 

m,  .376  ) 









Heavy  sledge  (swung). . 


n,  .374  I 
o,  .377 









Internal  Effects  of  Hammering  on  Metals. — Besides  the  surface  work  produced  by  hammers,  there 
is  some  hitherto  mysterious  and  as  yet  uninvestigated  internal  work  done  by  them.  If  an  iron  bar 
be  held  in  the  line  of  the  dip  of  the  magnetic  needle  and  struck  upon  the  upper  end  with  an  ordinary 
hammer,  it  will  become  polarized,  one  end  repelling,  the  other  end  attracting,  the  magnetic  needle. 
Reverse  the  bar  and  strike  it  on  the  opposite  end  as  many  blows  as  before  were  given,  and  both 
ends  will  attract  the  magnet.  Give  two  or  three  more  blows,  and  the  bar  shows  magnetic  effects  the 
reverse  of  those  first  obtained.  Something,  therefore,  has  occurred  in  the  bar  due  to  hammer-im- 
pact, and  the  recognition  of  this  makes  it  in  a  measure  apparent  why  the  compass  needle  in  iron 
ships  may  be  affected  in  consequence  of  the  tremor  to  which  the  vessel  is  subjected  owing  to  blows 
from  the  waves. 



These  magnetic  manifestations  seem  to  be  accompanied  with  internal  material  changes,  which 
sometimes  make  their  existence  too  clear  by  fractures  as  unexpected  as  they  are  dangerous.  In  the 
Engine  Works  at  Crewe,  England,  numerous  investigations  have  been  made  into  the  consequences  of 
blows  as  from  hammers  upon  cold  metals.  In  one  case  an  axle  of  a  locomotive  tender,  with  its 
wheels,  was  subjected  to  a  series  of  blows,  which  were  successive,  periodic,  and  adjusted.  The 
dimensions  of  the  axle  were  6  feet  ll£  inches  long  and  5|  inches  diameter  where  the  wheel  was 
keyed  on.  It  projected  S|  inches  beyond  the  wheel.  A  weight  of  60  lbs.  was  caused  to  fall  from  a 
height  of  5  feet  upon  the  same  part  of  the  axle.  In  the  case  of  an  iron  axle,  a  crack  manifested 
itself  after  6,128  blows,  and  the  axle  was  broken  by  9,843  blows.  When  the  axle  was  of  steel  and 
of  the  same  dimensions,  the  weight  struck  50,000  blows  from  a  height  of  5  feet.  Afterward  3,040 
blows  were  given  by  the  same  weight  falling  from  a  height  of  10  feet;  and  then  the  axle  broke  in 
two  pieces.  It  is  remarkable  that  in  this  case  there  were  no  previous  signs  of  injury,  the  sound 
caused  by  the  blow  previous  to  that  which  fractured  the  axle  being  as  clear  in  its  ring  as  that  emitted 
by  the  first  blow  struck.  Calculated  according  to  the  principle  already  detailed,  the  measure  of  the 
energy  expended  before  the  iron  axle  cracked  is  represented  by  6,128  x  60  x  5  =  1,838,400;  and 
after  being  cracked  and  before  the  fracture  by  3,715  x  60  x  5  =  1,114,500 ;  making  a  total  energy  of 
2,952,000.  Now,  before  the  steel  axle  was  fractured  there  was  expended  upon  it  first  an  energy  rep- 
resented by  50,000  x  60  x  5  =  15,000,000,  and  this  was  succeeded  by  3,040  x  60  x  10  =  1,824,000 ; 
i.  e.,  before  the  fracture  the  steel  axle  was  subjected  to  a  total  energy  of  16,824,000,  or  to  about  9 
times  the  hammering  given  to  the  iron  before  the  latter  cracked. 

Effects  of  Heavy  and  Liyht  Hammers. — An  inquiry  of  much  interest  with  respect  to  hammers  is : 
What  difference  is  produced  on  a  material  if  struck  by  a  light  hammer  moving  at  a  high  velocity, 
and  by  a  heavy  hammer  moving  at  a  low  velocity  ?  For  example :  Suppose  a  hammer  weighing  2 
lbs.  strikes  an  object  with  a  velocity  of  40  feet  per  second  ;  then  the  height  from  which  that  hammer 
must  have  fallen  under  the  action  of  gravity  only  would  be  24.845  feet.  The  work  done  would  there- 
fore be  represented  by  2  x  24.845  =  49.690  foot-pounds — say  50.  Again,  suppose  a  hammer  weigh- 
ing 10  lbs.  strikes  the  same  object  with  a  velocity  of  18  feet  per  second  ;  then  the  height  from  which 
that  hammer  must  have  fallen  under  the  action  of  gravity  only  would  be  5.0311  feet.  The  work 
done  therefore  would  be  represented  by  10  x  5.0311  =  50.311,  or  say  50  again. 

The  two  hammers  are  thus  said  to  have  the  same  amount  of  work  in  them,  or  to  be  capable  of 
doing  equal  work.  Yet  in  practice  their  effects  are  by  no  means  identical.  It  is  a  well-known  ex- 
perimental fact  in  mechanics  that  if  a  series  of  balls  be  suspended  as  shown  in  Figs.  2236  and  2237, 
and  if  one  ball  A  be  lifted  and  allowed  to  strike  the  row  of  balls,  no  matter  what  the  velocity  of  that 
ball  may  be,  but  one  ball  will  be  caused  to  swing  off  at  the  opposite  side  B.     If  two  balls  be  lifted 











/  1 


"v-     \ 

and  allowed  to  swing  against  the  rest,  as  in  Fig.  2237,  then  two  balls  will  be  thrown  off  at  the  other 
end ;  and  so  on.  No  increase  of  velocity  will  alter  the  corresponding  number  of  balls  thrown  off  at 
the  opposite  side,  though  it  will  the  distance  these  balls  travel.  Now  let  the  balls  in  line  represent 
the  atoms  or  molecules  of  a  body :  the  impinging  balls  will  be  hammers  of  different  masses.     The 





heavy  hammer,  so  to  speak,  transfers  its  mass  into  the  interior  of  the  struck  object,  while  the 
lighter  hammer,  acting  on  the  same  principle,  does  not  put  so  much  of  the  material  in  motion.  In 
the  case  of  riveting,  it  may  be  inferred  that  by  the  use  of  a  heavy  hammer  the  hot,  soft  rivet  might 
be  made  to  fill  in  the  recesses  of  the  rivet-hole,  while  the  lighter  hammer  would  simply  close  over 
and  finish  off  neatly  the  hammered  end,  without  a  cup-swage  being  put  over  it.  Similar  considera- 



tions  to  the  foregoing  underlie  the  use  of  light  and  heavy  projectiles  fired  at  high  aud  low  velocities 
from  cannon. 

Forms  of  Hammers. — Figs.  2238  to  2241  are  different  forms  of  engineers'  hammers,  varying 
chiefly  in  the  form  and  angle  the  pene  makes  to  the  head.  Figs.  2242  to  2245  are  plumbers'  ham- 
mers, Fig.  2242  being  used  both  as  a  hammer  and  as  a  swage.  Fig.  2246  is  a  mason's  hammer. 
Figs.  2247  and  2248  show  the  forms  used  by  boiler-makers.  Fig.  2249  is  a  cooper's  hammer,  and 
Fig.  2250  a  ship-carpenter's  claw-hammer.  Fig.  2251  is  a  coach-trimmer's,  and  Fig.  2252  a  slater's 
hammer.     Fig.  2253  is  a  fireman's  hatchet  or  tomahawk  hammer,  and  Fig.  2254  is  a  carpenter's 







mallet,  which  should  be  made  of  hickory,  the  sizes  being,  one  2{,  x  3  x  5  inches  long,  and  another 
about  3  x  3J  x  5^  inches  long,  the  handles  being  mortised  and  properly  wedged  to  the  head. 

Manipulation  of  the  Hammer, — The  operations  performed  by  the  hammer  may  be  classified  ass  1, 
driving  ;  2,  bending ;  3,  stretching  or  expanding.  The  first  two  are  comparatively  rude  operations, 
but  in  the  last  named  the  exercise  of  unusual  skill  and  judgment  is  required.  When  stretching  by 
means  of  the  hammer  is  resorted  to  for  the  purpose  of  altering  the  form  of  work  to  bring  it  to  a 
required  form,  regardless  of  straightness  and  flatness,  it  is  termed  "  pening,"  or  sometimes  "  pan- 
ing  ;  "  when  flatness  or  truth  is  the  end  sought,  the  operation  is  termed  straightening.  In  pening, 
very  light  strokes  are  given,  so  as  to  cause  the  effects  of  the  blows  to  remain  at  or  near  the  surface 
of  the  metal.  But  in  straightening,  heavier  blows  are  delivered,  and  the  effects  penetrate  the  work 
correspondingly  to  a  greater  depth.  The  principle  involved  in  the  operation  of  pening  is  that  of 
stretching  the  surface  receiving  the  blows,  which  causes  the  pened  Burface  to  lift  above  the  plane  of 




the  original  surface.  Thus,  suppose  a  plate  of  iron  to  be  bent  as  shown  in  Fig.  2255.  The  delivery 
of  light  blows,  as  denoted  by  the  small  circles  at  A,  would  stretch  that  side  of  the  plate  without 
affecting  the  opposite  surface,  and  by  elongating  it  cause  the  plate  to  straighten ;  or  if  the  pening 
were  sufficient,  the  plate  would  become  bent  in  the  opposite  direction,  the  convex  surface  becoming 
the  concave  one. 

The  hammer  used  by  plate-straighteners  and  saw-straighteners,  shown  in  Fig.  2256,  is  termed  a 
"  long  cross-face  " — "  long  "  because,  being  intended  to  be  used  as  a  sledge,  it  is  provided  with  a 
long  handle,  and  "  cross-face  "  because  the  length  of  the  face  on  one  end  stands  crosswise  with  the 



length  of  the  face  on  the  other.  This  hammer  causes  the  metal  to  rise  or  lift  in  front  of  it,  the 
direction  in  which  the  rise  takes  place  depending  upon  the  direction  in  which  the  length  of  the  ham- 
mer-face strikes  the  plate.  Suppose,  for  example,  that  we  strike  the  blows  shown  at  the  end  A  of 
the  plate  shown  in  Fig.  2257,  and  that  we  then  turn  the  hammer  upside  down  and  strike  the  blows 





denoted  by  the  marks  at  B  in  the  same  figure  (this  the  workman  can  perform  by  reversing  the 
hammer,  without  changing  his  position) ;  the  result  will  be  to  curl  up  the  plate  as  denoted  by  the 
dotted  lines.  This  effect  is  produced  by  two  causes,  the  first  of  which  is  the  shape  of  the  hammer- 
face,  and  the  second  is  the  direction  in  which  the  blows  fall.     Fig.  2258  represents  an  iron  plate 




with  one  each  of  the  blows  shown  in  Fig.  2257  delivered  upon  it,  at  B  and  C.  Then,  the  indenta- 
tion of  the  plate  being  denoted  by  the  full  line,  the  tension  caused  to  the  surrounding  iron  will  be 
indicated  by  the  dotted  lines.  It  will  be  noted  that  these  dotted  lines  are  in  each  case  longer  on  one 
side  of  the  mark  than  on  the  other ;  and  the  reason  is  that  the  effect  is  greater  on  that  side,  or  rather 
in  that  direction,  because  the  hammer  does  not  fall  vertically  upon  the  plate,  but  somewhat  aslant. 
If  the  plate  shown  in  Fig.  2257  be  turned  up  on  edge  so  as  to  appear  as  in  Fig.  2259,  the  direction 
in  which  the  hammer  would  travel  when  striking  the  blows  at  A  in  Fig.  2257  is  denoted  by  the 
arrows  B  in  Fig.  2259 ;  while  if  we  turn  up  the  same  plate  so  that  its  edge  D  in  Fig.  2258  will  ap- 
pear as  the  edge  D  in  Fig.  2260,  the  direction  of  the  blows  shown  at  B  inFig.  2257  will  be  denoted 
by  the  arrows  B  in  Fig.  2260 ;  so  that  both  the  shape  of  the  hammer-face  and  the  direction  of  the 
blow  conjointly  act  to  draw  or  bend  the  plate  in  the  required  direction.  If  we  take  a  ball-faced 
hammer,  the  effect  produced  will  be  as  shown  in  Fig.  2261,  in  which  the  circle  A  represents  the 
mark  left  by  a  ball-face  or  pene  hammer,  and  the  diverging  dotted  lines  show  the  effect  of  the  blow 
upon  the  surrounding  iron.  B  represents  a  blow  delivered  by  the  same  hammer,  which  while  falling 
traveled  also  in  the  direction  of  the  arrow  C,  the  direction  effects  of  the  blow  being  denoted  by  the 
dotted  lines. 

We  next  come  to  the  twist-hammer,  shown  in  Fig.  2262.  This  is  a  hand-hammer  with  the  two 
faces  standing  parallel  to  each  other,  but  diagonal  to  the  body  of  the  hammer ;  so  that,  by  turning 
the  handle  in  the  hand,  the  direction  of  the  hammer-marks  will  be  reversed.  Suppose,  for  example, 
that  in  Fig.  2263  the  outlines  represent  a  plate;  the  lines  slanting  one  way,  as  at  A,  will  represent 
hammer-marks  made  by  one  face,  and  those  slanting  the  other  way,  as  at  B,  marks  made  by  the 
other  face  of  the  hammer,  the  direction  or  line  in  which  the  hammer  fell  being  the  same  in  both 
cases.  By  very  little  moving  of  the  position  of  the  hammer-handle,  then,  and  by  turning  the  ham- 
mer as  required,  the  workman  can  place  the  hammer-marks  in  any  necessary  direction,  as  shown  by 



the  remaining  marks  in  Fig.  2263,  without  needing  to  change  his  position.  The  iron-worker  often 
employs  this  means  to  alter  the  form  of  girder-rods,  shafts,  etc.,  that  are  too  rigid  to  be  bent  by 
ordinary  hammer-blows,  as  well  as  to  close  and  refit  work.     Suppose,  for  instance,  the  strap  shown 


r-      '•"   '■ 


in  Fig.  2264  was  too  wide  at  A.  If  may  be  rested  on  a  bench  or  wooden  block  E  and  pened  at  the 
corner  C.  If,  however,  the  strap  had  a  sharp  instead  of  a  round  corner  at  C,  it  would  he  neces- 
sary to  rest  the  two  ends  of  the  strap-jaws  on  the  bench,  and,  using  the  ball  pene,  deliver  the  blows 
shown  by  the  marks  at  D.  In  either  ease,  the  effect  will  be  to  close  the  distance  between  the  jaws 
at  A.  The  reason  in  the  latter  case  for  pening  the  strap  in  the  middle  is  that,  since  the  pening  will 
tend  to  round  the  face  lengthwise,  tiling  out  the  pening  marks  will  tend  to  straighten  that  face,  and 
may  be  more  quickly  performed  ;  for,  if  we  were  to  pene  the  face  in  two  places,  the  iiling  out  of 
the  marks  would  aid  the  pening  to  round  the  face.  It  is  obvious  that,  were  the  jaws  too  narrow  at 
A,  pening  the  inside  crown  face  of  the  strap  would  widen  them.  The  Mows  should  fall  dead;  that 
is,  the  hammer  should  fall,  to  a  great  extent,  1>\  its  own  weight,  the  number  rather  than  the  force  of 
the  blows  being  depended  upon ;  hence  the  hammer-marks  will  not  be  deep.     This  is  of  especial  im- 









portance  when  pening  has  to  be  performed  upon  finished  work,  because,  if  the  marks  sink  deeply, 
proportionately  more  grinding  or  filing  is  required  to  efface  them ;  and  for  this  reason  the  force  of 
the  blows  should  be  as  near  equal  as  possible.  Another  and  a  more  important  reason,  however,  is 
that  the  effect  of  the  pening  does  not  penetrate  deeply ;  and  if  much  of  the  pened  surface  is  re- 
moved, the  effects  of  the  pening  will  be  also  removed ;  for,  as  a  rule,  the  immediate  effects  of  the 
blows  do  not  penetrate  deeper  than  about  one-thirty-second  of  an  inch.  While  the  work  is  being 
pened,  it  should  be  rested  upon  a  wood  or  a  lead  block,  and  held  so  that  the  part  struck  is  supported 
as  much  as  possible  by  the  block.  In  no  case  should  it  be  rested  upon  an  iron  or  any  hard-metal 
block,  as  that  would  tend  to  stretch  the  under  face,  and  partially  nullify  the  effects  of  the  pening. 

In  straightening  work  of  cast-iron,  pening  bears  an  important  part,  especially  in  the  case  of  iron 
patterns  or  light  iron  castings.     Suppose,  for  example,  that  Fig.  2265  represents  an  iron  casting,  and 













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O  0 


that  the  distance  A  from  the  centre  of  one  double  eye  to  that  of  the  other  was  too  short ;  by  pening 
the  arms  on  the  faces  denoted  by  B,  C,  and  in  the  place  denoted  by  B,  the  distance  A  could  easily 
be  made  correct.     If  the  width  at  A  were  too  great,  similar  pening  at  C,  D  would  be  required. 
The  skill  demanded  in  the  straightening  processes  consists  not  so  much  in  delivering  the  blows  as 


in  discovering  precisely  where  they  should  be  delivered,  because  one  misdirected  blow  increases  the 
error  in  the  plate  and  entails  the  necessity  of  many  properly  delivered  ones ;  and  though  the  whole 
plate  may  be  stiffened  by  the  gross  amount  of  blows,  yet  there  will  be  created  local  tensions  in  vari- 
ous parts  of  the  plate,  rendering  it  very  likely  to  spring  or  buckle  out  of  truth  again.  If,  for  ex- 
ample, we  take  a  plate  of  iron  and  hammer  it  indiscriminately  all  over  its  surface,  we  shall  find  it 
very  difficult  to  straighten  it  afterward,  not  only  on  account  of  the  foregoing  reasons,  but  for  the 
additional  and  most  important  one  that  the  effect  of  the  straightening  blows  will  be  less,  on  account 
of  the  hammered  surface  of  the  plate  offering  increased  resistance  to  the  effects  of  each  blow ;  and 
after  the  plate  is  straightened,  there  will  exist  in  it  conflicting  strains,  an  equilibrium  of  which  holds 
the  plate  straight,  but  the  weakening  of  any  of  which  will  cause  the  preponderance  of  the  others  to 
throw  the  plate  out  of  straight.  To  discover  where  it  is  necessary  to  apply  the  hammer,  the  operator 
(if  it  is  a  thin  plate)  rests  one  end  on  the  straightening  block  or  anvil,  and  supports  the  other  end 
with  one  hand  while  with  the  other  he  bends  the  plate.  The  unduly  expanded  parts  of  the  plate 
then  show  themselves  by  their  excessive  movement 

under  the  bending  process,  and  for  this  reason  are  2268. 

called  loose  places  ;  while  the  unduly  contracted  parts, 
which  are  called  tight  places,  offer  more  resistance  to 
the  movement,  and  therefore  move  less.  The  opera- 
tor requires  to  observe,  besides  the  location,  the  shape 
of  the  loose  place,  so  that  he  may  know  in  what  direc- 
tion the  length  of  the  hammer-face  should  meet  the 
plate  to  stretch  the  tight  places  in  the  proper  direc- 
tion. If  the  plate  is  too  heavy  and  strong  to  be  tested 
by  springing  it  with  the  hand,  it  is  held  or  rested  on 
edge,  when  the  shadows  upon  its  face  disclose  the  ex- 
panded and  contracted  places.  In  either  case  the  ham- 
mer is  similarly  applied.  An  example  is  shown  in  Fig. 
2266,  in  which  A  is  supposed  to  represent  a  loose  place,  and  B,  C,  and  D  tight  places.  The  ham- 
mer is  therefore  applied  at  B,  C,  and  D,  as  denoted  by  the  small  circles.  This  process,  however, 
induces  a  tight  place  at  E,  which  is  also  hammered. 

In  Figs.  2267  and  2268  is  shown  the  process  for  removing  kinks  or  bends  at  the  edge  of  the  plate, 
the  circular  lines  at  A  denoting  a  loose  place.  The  hammer  is  first  applied  as  at  B  ;  the  plate  is 
then  turned  over  and  hammered  as  at  c  in  Fig.  2268,  the  lengths  of  the  hammer-marks  being  in  the 
direction  shown. 

A  valuable  paper  on  the  hammer,  by  the  Rev.  Arthur  Rigg,  from  which  extracts  are  made  in  this 
article,  appears  in  the  Journal  of  the  Society  of  Arts,  xxiii.,  813.  J.  R.  (in  part). 

HAMMERS,  POWER.  Of  these  machines  there  are  three  principal  types:  1.  Drop-hammers,  in 
which  the  hammer  is  lifted  and  afterward  allowed  to  fall  by  its  own  gravitation,  delivering  its  blow 
after  the  manner  of  a  pile-driver.  2.  Trip-hammers,  in  which  the  hammer  is  lifted  by  a  cam  against 
the  compression  of  a  spring  or  elastic  cushion,  which  accelerates  the  fall  of  the  hammer,  and  hence 
the  force  of  the  blow  delivered,  when  the  hammer  arm  or  beam  is  released  from  the  action  of  the 
cam.  3.  Dead-stroke  hammers,  in  which  the  connection  between  the  hammer  and  the  mechanism 
driving  it  is  made  elastic,  so  as  to  enable  the  hammer  on  its  descent  to  increase  in  velocity  independ- 
ently of  the  speed  of  the  mechanism,  and  also  designed  to  prevent  the  full  shock  due  to  the  blow 
from  being  imparted  to  the  frame  and  other  portions  of  the  machine.  To  this  last  class  belong  the 
pneumatic  hammers. 

Drop-Hammers  have  become  almost  indispensable  for  the  manufacture  of  small  articles  of  iron 
and  steel,  such  as  parts  of  sewing-machines  and  fire-arms.  They  operate  in  connection  with  properly 
made  matrices  and  dies,  reproducing  almost  indefinitely  the  form  in  its  exactness,  and  leaving  the 
material  in  excellent  shape  for  subsequent  working.  Drop-dies  are  usually  made  of  refined  cast- 
steel,  and  they  are  often  strapped  with  tough  wrought-iron  shrunk  on  after  the  dies  are  otherwise 

Merrill's  Drop-Hammer  is  represented  in  perspective  in  Fig.  2269.  The  operating  mechanism  is 
shown  in  section  in  Fig.  2270.  The  hammer-head,  which  weighs  from  300  to  1,800  lbs.,  is  attached 
to  a  board  of  white  oak  B,  which  passes  up  between  two  smooth  friction-rolls  A  in  the  upper  portion 
of  the  machine.  These  rolls  revolve  in  opposite  directions.  The  shaft  upon  which  the  front  roll  is 
keyed  runs  in  eccentric  sleeves,  one  of  which  is  shown  at  C,  placed  in  stationary  boxes.  When  these 
sleeves  are  rotated  a  small  portion  of  a  circle,  the  front  roll  is  moved  nearer  to  or  farther  from  the  rear 
roll,  and  this  movement  is  effected  by  the  operator  by  means  of  the  rod  D,  which  is  connected  with 
a  treadle.  When  the  rolls  are  closed  together  and  pressed  against  the  board,  their  friction  on  each 
side  of  the  latter  raises  it,  and  thus  elevates  the  hammer ;  then,  when  the  rolls  are  separated,  the 
head  is  free  to  fall  by  its  own  gravity.  On  the  right  of  the  machine,  Fig.  2269,  is  shown  a  latch 
which  is  connected  with  the  treadle,  and  which  may  be  pivoted  at  any  elevation.  On  this  the  ham- 
mer rests  in  the  beginning,  and  when  the  workman  presses  down  the  treadle  he  pulls  back  this  latch, 
and  at  the  same  time  through  the  rod  D  separates  the  rolls.  The  hammer  then  falls.  The  instant 
the  blow  is  delivered,  the  operator  removes  his  foot  from  the  treadle,  the  drop-rod  then  falls,  and 
the  eccentric  sleeve  turning  the  front  roll,  aided  by  the  pull  of  the  belt,  is  forced  against  the  board, 
raising  the  hammer  up  again.  If  it  be  desired  to  give  a  series  of  heavy  blows,  the  latch  is  thrown 
back,  and  the  hammer  is  allowed  to  rise  until  it  strikes  a  projection  on  the  drop-rod.  It  thus  lifts 
the  latter,  causes  a  separation  of  the  rolls,  and  falls.  By  this  arrangement  the  hammer  may  be 
made  to  follow  the  motion  of  the  foot,  and  blows  of  any  degree  of  lightness  or  shortness  may  be 

The  Hoichkiss  &  Stiles  Drop-Hammer. — The  working  portions  of  this  hammer  are  represented  in 



^      ^  £^& 


2278.  »A  . 

Fig.  2271.  A  board  is  attached  to  the  head,  as  in  the  preceding  example,  and  passes  between  fric- 
tion-rolls. Motion  from  one  to  the  other  of  the  latter  is  communicated  by  cog-wheels  B.  The  teeth 
are  always  engaged,  and  hence  the  revolution  is  constant ;  but  in  order  "to  cause  the  griping  of  the 
board,  the  shaft  of  one  wheel,  and  consequently  the  roll  thereon,  is  moved  closer  to  the  other.  The 
teeth  of  the  wheels  are  sufficiently  long  to  admit  of  this  movement.    -This  sliding  motion  is  effected 



by  an  eccentric  C  connected  with  a  lever  D.     Clamps  G  are  provided  to  enable  the  operator  to  hold 
the  hammer  at  will. 

In  making  drop-forgings,  the  metal  is  heated  and  placed  in  the  lower  die,  but  not  in  such  a  quan- 


tity  as  to  fill  the  latter.     As  the  drop  falls  the  blow  forces  the  material  into  all  the  recesses  of  the 
mould,  of  which  the  exact  shape  is  reproduced.     It  is  quite  common  to  place  the  hot  metal  above 



the  die  and  drive  it  down,  doubling  it  up,  so  to  speak.     This  is  bad  practice,  as  the  air  in  the  die 
becomes  tremendously  compressed,  and  forces  its  way  out,  scoring  the  cast-steel  of  the  latter  almost 


as  sharply  as  if  done  by  a  file.  Again,  but  a  single  blow  should  be  delivered,  as  the  first  stroke 
usually  spreads  out  a  thin  sheet  of  metal  on  the  surface  of  the  die,  which  rapidly  cools.  If  this  be 
struck  by  the  hammer,  not  only  will  the  forging  be  thrown  out  of  shape,  but  the  die  itself  is  liable 
to  be  injured. 

Trip-Hammers. — Figs.  2272  and  2273  represent  a  small  trip-hammer,  such  as  is  commonly  used 
in  forging  spindles  and  bolts,  and  for  swaging  various  other  kinds  of  small  work.  A  is  the  driving- 
pulley,  with  a  flange  on  each  side  to  guide  the  belt  while  running  loose.  This  pulley  is  attached  to 
the  cam-shaft,  upon  the  other  end  of  which  is  the  balance-wheel  E.  c  is  a  foot-lever,  connected 
with  the  catch  b  by  a  rod  and  spring,  by  means  of  which  the  hammer  can  be  stopped  or  started 
without  shipping  the  belt.  F  is  a  bed  of  timbers  bolted  together  to  form  a  support.  G  is  the  post 
in  which  the  hammer-block  is  placed,  and  usually  extends  4  or  5  feet  into  the  ground,  /is  the  rock- 
er, adjusted  by  screws  and  bolts,  so  that  the  hammer  can  be  set  at  any  taper.  S  is  a  heavy  cast-iron 
plate  to  which  all  other  parts  are  connected,  and  which  is  bolted  firmly  to  the  timbers  below. 

Figs.  2274  and  2275  represent  another  form  of  trip-hammer,  in  which  b  is  the  lifting-cam. 

Dead-stroke  Hammers. — The  Palnu  r  Power-Spring  Hammer  is  shown  in  Fig.  2276.  The  hammer 
slides  in  guides  provided  in  the  frame,  motion  being  given  to  it  by  means  of  a  spring  pivoted  at  its 
centre  and  operated  by  a  crank  and  connecting-rod,  as  shown. 

The  Bradley  Cushioned  Hamrm  r  is  shown  in  Fig.  2277.  The  upper  hammer  A  is  bolted  to  the  tube 
B,  which  passes  through,  and  is  carried  by  a  tasting  pivoted  at  C  in  bearing-blocks  which  may  be 
adjusted  in  height  (by  means  of  the  set-screw  a  and  hand-wheel  b)  so  that  the  face  of  the  upper 
hammer  may  meet  the  face  of  the  work  fair,  notwithstanding  variations  in  its  thickness.  Pivoted 
also  at  C  is  a  triangular  frame  having  the  two  sockets  II  for  the  reception  of  rubber  cushions  or 
springs  F  (!.  This  frame  receives  motion  from  the  connecting-link  //,  to  which  it  is  pivoted.  H 
receives  motion  from  an  eccentric  upon  the  shaft  J.  As  this  frame  lifts,  it  throws  the  tube  against 
the  rubber  cushion  E,  which  causes  the  motion  of  B  to  be  reversed  with  considerable  force. 

Pneumatic  Hammer. — Fig.  2278  represents  a  sectional  view  of  the  air-cylinder  of  an  improved 
atmospheric  hammer  invented  by  M.  Chenot,  and  exhibited  at  the  French  International  Exposition 
of  1878.  When  the  crank  A  rises,  it  draws  with  it  the  pistons  B  and  C.  Piston  B  causes  an  ex- 
pansion in  chamber  1.  Piston  C  compresses  the  air  in  chamber  2,  and  produces  expansion  or  partial 
vacuum  in  chamber  8.  These  effect-  unite  to  cause  the  entire  cylinder  D  to  rise,  thus  elevating  the 
hammer  E.  The  cylinder  D  continues  its  rapid  upward  motion  until  the  crank  passes  the  point  F. 
Then  the  combined  action  of  the  ascending  cylinder  and  descending  pistons  produces  a  strong  com- 
pression of  the  air  in  chambers  1  and  ?>,  and  this  air  expanding  drives  down  the  cylinder  and  hammer 
with  great  force  upon  the  anvil.  Without  the  interposing  air-cushion  which  always  exists  between  the 
working  parts,  it  is  evident  that  this  machine  would  be  subject  to  severe  and  injurious  shocks ;  but 
these  seem  to  be  avoided  by  the  means  stated.  The  movement  of  the  hammer  is  controlled  by 
mechanism  connecting  with  the  brake  0. 

11 AMMERS,  STEAM,  DIRECT-ACTING.  The  conditions  fulfilled  by  steam  as  a  driving  medium 
for  hammers  are  summed  up  by  Mr.  J.  Richards,  in  his  "Workshop  Manipulation,"  as  follows:  1. 
The  power  is  connected  to  the  hammer  by  means  of  the  least  possible  mechanism,  consisting  only  of 
a  cylinder,  a  piston  and  slide-valve,  induction-pipe,  and  throttle-valve;  these  few  details  taking  the 
place  of  a  steam-engine,  shafts,  belts,  cranks,  springs,  pulleys,  gearing — in  short,  all  such  details  as 
are  required  between  the  hammer-head  and  the  steam-boiler,  in  the  case  of  power  hammers.  (Sec 
Hammers,  Power.)  2.  The  steam  establishes  the  greatest  possible  elasticity  in  the  connection  be- 
tween a  hammer  and  the  driving-power,  and  at  the  same  time  serves  to  cushion  the  blows  at  both 
the  top  and  bottom  of  the  stroke,  or  on  the  top  only,  as  occasion  may  require.  3.  Each  blow  given  is 
an  independent  operation,  and  can  be  repeated  at  will,  while  in  other  hammers  such  changes  can  only 
be  made  throughout  a  series  of  blows  by  gradually  increasing  or  diminishing  their  force.  4.  There 
is  no  direct  connection  between  the  moving  parts  of  the  hammer  and  the  framing,  except  lateral 
guides  for  the  hammer-head;  the  steam  being  interposed  as  a  cushion  in  the  line  of  motion,  this 
reduces  the  required  strength  and  weight  of  the  framing  to  a  minimum,  and  avoids  positive  strains 
and  concussion.  5.  The  range  and  power  of  the  blows,  as  well  as  the  time  in  which  they  are  de- 
livered, are  controlled  at  will ;  this  constitutes  the  greatest  distinction  between  steam  and  other 
hammers,  and  the  particular  advantage  which  has  led  to  their  extended  use.  6.  Power  can  be  trans- 
mitted to  steam-hammers  through  a  small  pipe,  which  may  be  carried  in  any  direction,  and  for  almost 
any  distance,  at  a  moderate  expense,  so  that  hammers  may  be  placed  in  such  positions  as  will  best 
accommodate  the  work,  and  without  reference  to  shafts  or  other  machinery.  7.  There  is  no  waste 
of  power  by  slipping  belts  or  other  frictional  contrivances  to  graduate  motion ;  and  finally,  there  is 
no  machinery  to  be  kept  in  motion  when  the  hammer  is  not  at  work. 

Steam-hammers  are  divided  into  two  classes — one  class  having  the  valves  moved  by  hand,  and  the 
other  with  automatic  valve  movement.  The  action  of  steam-hammers  may  also  be  divided  into  what 
are  termed  elastic  blows  and  dead  blows.  In  operating  by  elastic  blows,  the  steam-piston  is  cushioned 
at  both  the  up  and  down  stroke,  and  the  action  of  a  steam-hammer  corresponds  to  that  of  a  helve 
trip-hammer,  the  steam  filling  the  office  of  a  vibrating  spring ;  in  this  case  a  hammer  gives  a  quick 
rebounding  blow,  the  momentum  being  only  in  part  spent  upon  the  work,  and  partly  arrested  by 
cushioning  on  the  steam  in  the  bottom  of  the  cylinder  under  the  piston.  Apart  from  the  greater 
rapidity  with  which  a  hammer  may  operate  when  working  on  this  principle,  there  is  nothing  gained, 
and  much  lost ;  and  as  this  kind  of  action  is  imperative  in  any  hammer  that  has  a  "  maintained  or 
positive  connection  "  between  its  reciprocating  parts  and  the  valve,  it  is  perhaps  fair  to  infer  that 
one  reason  why  most  automatic  hammers  act  with  elastic  blows  is  either  because  of  a  want  of 
knowledge  as  to  a  proper  valve  arrangement,  or  the  mechanical  difficulties  in  arranging  valve-gear  to 
produce  dead  blows.  In  working  with  dead  blows,  no  steam  is  admitted  under  the  piston  until  the 
hammer  has  finished  its  down  stroke,  and  expended  its  momentum  upon  the  work.     So  different  is 



the  effect  produced  by  these  two  plans  of  operating,  that  on  most  kinds  of  work  a  hammer  of  50  lbs. 
working  with  dead  blows  will  perform  the  same  duty  that  one  of  100  lbs.  will  when  acting  by  elastic 
or  cushioned  blows.     This  difference  between  dead  and  elastic  strokes  is  so  important,  that  it  has 

served  to  keep  hand-moved  valves  in  use  in  many  cases  where  much  could  be  gained  by  employing 
automatic-acting  hammers. 

Some  makers  of  steam-hammers  have  so  perfected  the  automatic  class,  that  they  may  be  instantly 



changed  so  as  to  work  with  either  dead  blows  or  elastic  blows  at  pleasure,  thereby  combining  all  the 
advantages  of  both  principles.  This  brings  the  steam-hammer  where  it  is  hard  to  imagine  a  want  of 
further  improvement.  The  valve-gearing  of  automatic  steam-hammers,  to  fill  the  two  conditions  of 
allowing  a  dead  or  an  elastic  blow,  furnishes  one  of  the  most  interesting  examples  of  mechanical 
combination.  It  was  stated  that  to  give  a  dead  or  stamp  stroke,  the  valve  must  move  and  admit 
steam  beneath  the  piston  after  the  hammer  has  made  a  blow  and  stopped  on  the  work,  and  that  such 
a  movement  of  the  valve  could  not  be  imparted  by  any  maintained  connection  between  the  hammer- 
head and  valve.  This  problem  is  met  by  connecting  the  drop  or  hammer-head  with  some  mechanism 
which  will,  by  reason  of  its  momentum,  continue  to  move  after  the  hammer-head  stops.  This  me- 
chanism may  consist  of  various  devices.  Messrs.  Massey  in  England,  and  Messrs.  Ferris  &  Miles  in 
this  country,  employ  a  swinging  wiper-bar,  which  is  by  reason  of  its  weight  or  inertia  retarded,  and 
does  not  follow  the  hammer-head  closely  on  the  down  stroke,  but  swings  into  contact  and  opens  the 
valve  after  the  hammer  has  come  to  a  full  stop.  By  holding  this  wiper-bar  continuously  in  contact 
with  the  hammer-drop,  elastic  or  rebounding  blows  are  given  ;  and  by  adding  weight  in  certain  posi- 
tions to  the  wiper-bar,  its  motion  is  so  retarded  that  a  hammer  will  act  as  a  stamp  or  drop.  A  Ger- 
man firm  employs  the  concussion  of  the  blow  to  disengage  valve-gear,  so  that  it  may  fall  and  effect 
this  after-movement  of  the  valves.  Other  engineers  effect  the  same  end  by  employing  the  momentum 
of  the  valve  itself,  having  it  connected  to  the  drop  by  a  slotted  or  yielding  connection,  which  allows 
an  independent  movement  of  the  valve  after  the  hammer  stops. 

Another  principle  to  be  noticed  in  connection  with  hammers  and  forging  processes  is  that  of  the 
inertia  of  the  piece  operated  upon — a  matter  of  no  little  importance  in  the  heavier  kinds  of  work. 
When  a  piece  is  placed  on  an  anvil,  and  struck  on  the  top  side  with  a  certain  force,  the  bottom  or  anvil 
side  of  the  piece  does  not  receive  an  equal  force.  A  share  of  the  blow  is  absorbed  by  the  inertia  of 
the  piece  struck,  and  the  effect  on  the  bottom  side  is,  theoretically,  as  the  force  of  the  blow,  less  the 
cushioning  effect  and  the  inertia  of  the  pieces  acted  upon.  In  practice  this  difference  of  effect  on 
the  top  and  bottom,  or  between  the  anvil  and  hammer  sides  of  a  piece,  is  much  greater  than  would 
be  supposed.  The  yielding  of  the  soft  metal  on  the  top  cushions  the  blow  and  protects  the  under 
side  from  the  force.  The  effect  produced  by  a  blow  struck  upon  hot  iron  cannot  be  estimated  by  the 
force  of  the  blow;  it  requires,  to  use  a  technical  term,  a  certain  amount  of  force  to  "start"  the 
iron,  and  anything  less  than  this  force  has  but  little  effect  in  moving  the  particles  and  changing  the 
form  of  a  piece. 

Another  object  gained  by  equal  action  on  both  sides  of  large  pieces  is  the  quality  of  the  forgings 
produced,  which  is  generally  improved  by  the  rapidity  of  the  shaping  processes,  and  injured  by  too 
frequent  heating.  To  attain  a  double  effect,  and  avoid  the  loss  pointed  out,  Mr.  Ramsbottom  de- 
signed  what  may  be  called  compound  hammers,  consisting  of  two  independent  heads  or  rams  moving 
in  opposite  directions,  and  acting  simultaneously  upon  pieces  held  between  them.  It  would  be  in- 
ferred that  the  arrangement  of  these  double-acting  hammers  must  necessarily  be  complicated  and 
expensive,  but  the  contrary  is  the  fact  The  rams  are  simply  two  masses  of  iron  mounted  on  wheels 
that  run  on  ways,  like  a  truck,  and  the  impact  of  the  hammers,  so  far  as  not  absorbed  in  the  work, 
is  neutralized  by  each  other.  No  .-hoi  k  or  jar  is  communicated  to  framing  or  foundations,  as  in  the 
case  of  single-actim:  hammers  thai  have  fixed  anvils.  The  same  rule  applies  in  the  back  stroke  of 
the  hammers,  as  the  links  which  move  them  are  connected  together  at  the  centre,  where  the  power  is 
applied  at  right  angles  to  the  line  of  the  hammer  movement.  The  links  connecting  the  two  hammers 
constitute,  in  effect,  a  toggle-joint,  the  steam-piston  being  attached  where  they  meet  in  the  centre. 
The  steam-cylinder  which  moves  the  hammers  is  set  in  the  earth  at  some  depth  below  the  plane  upon 


11 -X  X  X  A  X  SSXijasjS 

;  *£\&cg>Ayo^c& 


which  they  move,  and  even  when  the  heaviest  work  is  done  there  is  no  perceptible  jar  when  one  is 
standing  near  the  hammers,  as  there  always  is  with  those  which  have  a  vertical  movement  and  are 

The  Xasmyth  St  earn- Hammer  is  one  of  the  best-known  forms  of  this  machine.  In  Fig.  2279  the 
hammer-block,  valve-gear,  and  other  working  parts  are  disposed  in  the  positions  which  they  occupy 
at  the  termination  of  a  stroke.     Fig.  2280  is  a  general  plan  corresponding  to  the  above. 

Fig.  2281  is  an  end  elevation,  and  Fig.  2282  a  vertical  transverse  section  of  the  machine. 



Fig  2283  is  a  sectional  elevation  of  a  portion  of  the  machine,  showing  the  positions  of  the  ham- 
mer-block, valve-gear,  and  other  working  parts  when  the  hammer  is  raised  for  a  fresh  stroke. 

Theframin"  of  the  steam-hammer  consists  of  two  strong  cast-iron  standards  A  A,  bolted  and 


further  secured  by  keys  to  a  broad  base-plate 
B  B,  imbedded  in  the  solid  masonry  forming  part 
of  the  floor  of  the  forge.  The  standards  are 
surmounted,  and  their  upper  extremities  united, 
by  a  species  of  entablature  C,  in  which  the  steam- 
passages  and  valve-face  are  formed,  and  to  the 
upper  surface  of  which  the  steam-cylinder  D  is 
bolted.  The  piston-rod  E  is  fitted  to  work  ver- 
tically through  a  stuffing-box  in  the  centre  of  this 
entablature,  and  its  lower  extremity  is  directly 
attached  to  the  mass  of  cast-iron  F,  forming  the 
hammer-block,  which  is  guided  to  a  strictly  ver- 
tical and  rectilinear  course  by  being  made  to  work  freely  in  planed  guides  formed  on  the 
surfaces  of  the  standards  A  A.     The  hammer  a  itself  is  inserted  into  a  dovetail  recess  in  the 




of  the  block  F,  where  it  is  retained  by  a  wooden  packing  and  iron  wedges ;  while  the  anvil  b  is  in  a 
similar  manner  secured  to  the  anvil-block  Or. 

Steam  is  led  to  the  machine  by  the  steam-pipe  II ;  a  throttle  or  shut-off  valve  c,  Fig.  2283,  in- 
closed within  the  valve-box  I,  being  situated  close  to  its  junction  with  the  main  steam-valve  chest  J, 
and  brought  within  the  control  of  the  attendant  workman  by  means  of  the  rod  and  lever  d  d.  The 
alternate  admission  of  the  steam  into  the  cylinder  by  the  port/,  and  its  escape  therefrom  by  the 
passage  </  and  waste  steam-pipe  K,  are  regulated  by  means  of  the  slide-valve  c,  which  may  either  be 
worked  by  hand,  or,  through  the  intervention  of  self-acting  mechanism,  by  the  action  of  the  machine 
itself.  The  piston  L,  which  is  strongly  constructed  of  malleable  iron,  is  fitted  with  a  single  packing- 
ring,  works  steam-tight  within  the  cylinder  D,  and  is  attached  by  the  piston-rod  E  to  the  hammer-block 

F.  Steam  acting  beneath  the  piston  raises  the  ham- 
mer, and  by  opening  the  communication  between  the 
under  side  of  the  piston  and  the  external  atmos- 
phere, the  action  of  gravity  causes  the  hammer  to 
descend  upon  the  work  placed  on  the  anvil. 

The  mode  adopted  for  connecting  the  piston-rod 
to  the  hammer-block  consists  in  placing  in  a  cylin- 
drical recess  formed  in  the  body  of  the  hammer- 
block,  and  under  the  knob  i,  on  the  end  of  the  pis- 
ton-rod, a  series  of  pieces  of  hard  wood,  or  other 
slightly  elastic  material,  as  in  Fig.  2281.  The  effect 
of  this  arrangement  is  to  allow  the  momentum  of 
the  piston  and  piston-rod  to  expend  itself  in  a  com- 
paratively gradual  manner.  The  connection  of  the 
piston-rod  and  hammer-block  is  secured  by  means  of 
the  two  keys  A4  A4,  driven  very  firmly  above  the  knob 
or  button  j,  a  layer  or  two  of  the  elastic  material 
being  interposed  for  the  purpose  of  neutralizing  any 
shock  in  the  contrary  direction. 

We  shall  now  proceed  to  describe  the  mechanism 
by  which  the  height  of  the  fall  of  the  hammer,  and 
consequent  intensity  of  the  blow,  may  be  modified 
according  to  circumstances,  and  the  machine  made 
perfectly  self-acting. 

The  requisite  alternating  motion  of  the  steam- 
valve  e  is  produced  in  the  following  manner:  The 
valve-spindle  /  is  prolonged  upward  and  attached  to 
a  small  solid  piston  m,  working  within  a  short  cyl- 
inder M,  bolted  to  the  main  steam-cylinder  I).  A 
small  portion  of  steam  is  supplied  above  the  piston 
///  by  a  slender  copper  tube  n,  communicating  with 
the  steam-valve  chest  J ;  by  this  arrangement  it  will 
be  seen  that,  unless  counteracted  by  some  superior 
force,  the  pressure  of  the  steam  upon  the  piston  m 
will  tend  to  keep  the  valve  c  constantly  depressed,  in 
^"y        ^\\jjr  *~1 —  I        j     w'hich  position  the  steam-port  /  is  full  open.     This 

O     — r —  „       I  i  I     counteracting  force  is  supplied  by  the  action  of  the 

hammer  itself ;  for,  by  means  of  the  tappet  N  (which 
is  bolted  to  the  hammer-block),  coming  into  sliding 
contact,  when  the  latter  is  raised,  with  the  small 
friction-roller  o,  mounted  on  the  end  of  a  bent  lever 
0  O,  the  screwed  rod  F,  which  is  jointed  to  the  op- 
posite end  of  that  lever,  is  depressed,  and  that  motion 
being  communicated  to  the  valve-spindle  /,  through 
the  intervention  of  the  connecting-rod  Q  and  valve- 
lever  B,  the  steam-valve  e  is  raised,  thus  cutting  off 
all  further  ingress  of  steam  under  the  piston,  and 
almost  at  the  same  instant  permitting  the  escape  of 
that  which  had  served  to  raise  the  hammer.  By 
this  simple  contrivance  the  upward  motion  of  the 
hammer  is  made  the  agent  for  its  own  control  in 
that  respect.  By  comparing  the  relative  positions 
of  the  parts  referred  to,  as  exhibited  in  Figs.  2279 
and  2283,  the  nature  of  the  motion  above  described 
will  be  at  once  most  fully  understood.  To  obviate  the  injurious  effects  of  the  shock  of  the  tappet 
N  against  the  lever  0,  a  connection  is  provided  at  />,  on  a  similar  principle  to  that  formerly  described 
in  reference  to  the  connection  of  the  piston-rod  and  the  hammer-block ;  and  in  order  to  restrict  the 
dow  nward  travel  of  the  valve  to  the  proper  point,  a  check  or  bujf'er-box  S  is  provided,  consisting  of 
a  small  cylinder  bolted  firmly  to  the  framing  of  the  machine,  within  which  a  circular  nut,  screwed  on 
the  lower  end  of  the  rod  F,  works  as  a  piston,  a  few  leather  washers  being  interposed  between  the 
latter  and  the  closed  or  upper  end  of  the  cylinder.  From  the  above  description  it  will  be  obvious 
that  the  lift  of  the  hammer,  and  consequent  intensity  of  the  blows,  depends  simply  upon  the  position 
of  the  lever  0,  in  relation  to  that  of  the  hammer-block  when  at  its  lowest  point.     The  rod  F,  which 



conveys  the  action  of  the  lever  0  to  the  valve-lever  R,  is  susceptible  of  rotatory  as  well  as  vertical 
motion.  This  motion  of  rotation  is  imparted  to  it  by  means  of  a  handle  fixed  to  a  short  axis,  work- 
ing in  a  bracket  T  bolted  to  the  framing,  and  actuating  a  pair  of  small  bevel-wheels  q  q.  The  nut 
through  which  the  screw  works  forms  the  point  of  attachment  between  the  rod  P  and  the  lever  0, 
the  connection  being  effected  by  means  of  a  short  intermediate  rod  for  the  sake  of  insuring  parallel- 
ism of  motion.  A  pair  of  small  spur-wheels  r  r  (through  the  first  of  which  the  rod  P  works  by 
means  of  a  sunk  feather)  serve  to  transmit  the  angular  motion  of  the  rod  P  to  a  similar  screwed  rod 
V,  situated  parallel  to  and  at  a  short  distance  from  the  former ;  the  nut  of  the  screw  U  forms  the 
fulcrum  or  centre  of  motion  of  the  lever  0,  and  the  pitch  of  the  threads  of  both  screws  being  equal, 
though  formed  in  contrary  directions  to  each  other,  it  is  obvious  that,  on  turning  the  handle,  the 
lever  0  and  all  its  appendages  will  be  simultaneously  raised  or  depressed,  and  consequently  the  lift 
of  the  hammer  regulated  to  any  required  extent,  and  its  amount  altered  with  the  utmost  ease  and 
precision.  The  pin  which  forms  the  centre  of  motion  of  the  lever  0  is  protected  and  secured  from 
lateral  strains  by  the  cast-iron  guides  Trand  IF,  seen  most  distinctly  in  the  sectional  plan,  Fig.  2280. 

A  most  essential  part  of  the  self-acting  gear  remains  yet  to  be  noticed.  It  is  obvious  that,  were 
no  provision  made  for  the  retention  of  the 
steam-valve  in  the  position  into  which  it  is 
thrown  by  the  upward  motion  of  the  hammer- 
block,  the  latter  would  not  be  permitted  to 
have  its  due  effect  in  the  accomplishment  of 
its  work  ;  for,  as  soon  as  it  descended  so  far 
as  to  relieve  the  end  of  the  lever  0  from  con- 
tact with  the  tappet  A7,  the  valve  would  re- 
sume the  position  into  which  it  is  constantly 
solicited  by  the  action  of  the  sfeam-spri/tf/  at 
M,  and  the  descent  of  the  blow  would  be  im- 
peded by  the  return  of  the  steam  into  the  cyl- 
inder before  the  hammer  had  completed  its 
fall.  To  obviate  this  inconvenience,  a  simple 
but  most  effectual  contrivance  has  been  ap- 
plied. Toward  the  lower  extremity  of  the 
valve-screw  P  a  shoulder  is  formed,  against 
which  a  short  lever  w,  called  the  trigger,  is 
constantly  pressed  by  the  spring  x,  so  that 
when  the  rod  P  is  depressed  by  the  action  of 
the  lever  0,  it  is  arrested  by  the  trigger  and 
retained  in  that  position  until  the  blow  has 
been  struck.  To  release  the  valve-screw  from 
the  trigger,  and  so  permit  the  return  of  the 
valve  into  the  position  requisite  for  effecting 
a  fresh  stroke,  the  following  mechanism  has 
been  adopted :  On  the  front  of  the  hammer- 
block,  Figs.  2279  and  2283,  a  lever  X,  called 
the  latch-levo;  is  fitted  to  work  freely  on  a 
pin  passing  through  the  body  of  the  hammer- 
block.  That  portion  of  the  latch-lever  which 
is  most  remote  from  the  valve-gear  is  consid- 
erably heavier  than  the  opposite  end,  and  is 
constantly  pressed  upward  by  means  of  a 
spring.  The  lighter  end  is  brought  into  con- 
tact with  a  long  bar  s  s,  called  the  parallel  bar, 
the  extremities  of  which  are  suspended  upon 
two  small  bell-cranks  1 1,  whose  other  arms 
are  connected  by  means  of  a  slender  rod  u, 
Fig.  2282,  forming  a  species  of  parallel  mo- 
tion, for  the  purpose  of  adapting  this  gear 
to  come  into  efficient  operation  at  whatever 
point  in  the  range  of  the  hammer  its  blow 
may  be  arrested.  A  small  connecting-rod  v, 
between  the  lower  bell-crank  and  a  short  lever  on  the  axis  of  the  trigger  w,  completes  this  part  of 
the  mechanism.  The  action  of  this  gear  is  of  a  very  peculiar  nature,  and  is  admirably  adapted  to 
fulfill  the  object  intended.  At  the  instant  the  hammer  gives  a  blow  to  the  work  upon  the  anvil,  the 
effect  of  the  concussion  is  to  cause  the  momentum  of  the  heavy  end  of  the  lever  X  to  overcome  the 
upward  pressure  of  the  spring,  and  thereby  to  protrude  its  opposite  end  against  the  edge  of  the  par- 
allel bar  s,  which  motion,  though  but  slight  in  amount,  is  yet  adequate,  through  the  arrangements 
above  described,  to  throw  back  the  trigger  from  contact  with  the  valve-screw,  and  leave  the  latter 
free  to  obey  the  impulse  of  the  steam-spring  in  the  readjustment  of  the  valve  into  its  original  position. 

The  Ferris  db  Miles  Steam-Hammer. — In  Fig.  2284  is  shown  a  steam-hammer  of  modern  design, 
constructed  by  Messrs.  Ferris  &  Miles.  The  hammer  has  a  weight  of  head  of  700  lbs.  Several 
peculiarities  of  design  will  be  noticed,  the  most  striking  of  them  being  that  the  head  A  is  set  at  an 
angle  in  the  frame.  The  die  C  is  of  the  oblong  form  shown  in  the  drawing,  as  well  as  that  of  the 
anvil-die  D.  The  object  of  this  arrangement  is  to  enable  the  workman,  after  drawing  out  his  work 
across  the  short  way  of  the  die,  to  turn  it  and  finish  it  lengthwise  without  being  inconvenienced  by  the 



frame.  By  this  means  skew  and  T-shaped  dies  can  be  dispensed  with,  and  the  full  surface  of  the 
ram  utilized.  The  latter  is  moved  between  the  guides  E  E,  and  held  in  place  by  the  steel  plate  F, 
bolted  through  the  frame  B.  The  valve  G  is  a  plain  cylinder  of  cast-iron,  enlarged  at  each  end  to 
work  in  the  cylindrical  seats  H  H,  in  which  the  ports  1 1  are  placed.  Steam  is  admitted  through  the 
valve  J,  and  circulates  round  the  valve  G  between  the  seats.  The  exhaust-chamber  K  is  below  the 
cylinder,  which  therefore  drains  condensed  steam  into  it  at  each  stroke  through  the  lower  steam- 
port.  The  exhaust  above  the  piaton  passes  down  through  the  interior  of  the  valves,  as  shown  by  the 
arrow  on  the  drawing.  The  valve-stem  L  is  connected  with  the  valves  in  the  exhaust-chamber.  No 
stuffing-box  is  therefore  required,  there  being  only  atmospheric  pressure  on  each  side  of  it.  This 
combination  enables  the  valve  to  be  so  perfectly  balanced  that  it  will  drop  by  its  own  weight  while 
under  steam. 

The  automatic  motion  is  obtained  by  an  inclined  plane  M,  upon  the  ram  A,  which  actuates  the 
rocker  JV,  the  outer  arm  of  which  is  connected  by  a  link  to  the  valve-stem,  and  thus  gives  motion  to 
the  valve!  The  valve  is  caused  to  rise  in  the  up-strokc  by  means  of  the  rocker  JV,  and  its  connec- 
tions, through  the  inclined  plane.  The  steam  is  thus  admitted  to  the  top,  which  drives  down  the 
piston,  while  the  valve  and  connections  follow  by  gravity,  thus  reducing  considerably  the  friction  and 
wear  upon  the  valves.  In  very  quick  work  the  fall  of  the  valves  may  be  accelerated  by  the  aid  of  a 
Bpring;  or  it  may  be  retarded  in  heavy  work  by  friction-springs,  so  as  to  obtain  a  heavier  blow  by  a 
fuller  admission  of  steam.  For  general  work,  however,  the  arrangement  shown  is  perfectly  effective, 
and  as  the  rocker  N  is  hung  upon  the  adjustment  lever  P,  any  required  variation  can  be  obtained  by 
the  movement  of  the  lever.  Single  blows  can  be  struck  with  any  degree  of  force,  or  a  rapid  succes- 
sion of  constant  or  variable  strokes  may  be  given. 

The  anvil  0  rests  upon  a  separate  foundation,  in  order  to  reduce  the  effect  of  concussion  upon  the 


frame.  Fig.  2284  illustrates  the  arrangement.  The  bed  is  long,  extending  beyond  the  hammer  on 
each  side  so  as  to  give  plenty  of  area,  and  the  ends  are  left  open  for  convenient  access  in  case  the 
anvil  should  settle  and  require  readjustment. 

The  Sellers  Steam-Hammer.— In  a  single-acting  steam-hammer  the  gross  force  of  the  blow  struck 
is  that  due  to  the  weight  of  the  die  or  hammer,  the  piston-rod  and  piston,  and  the  height  from  which 
they  fall ;  the  force  of  the  blow  being  regulated  by  varying  the  length  of  the  stroke,  or,  in  other 



words,  the  height  to  which  the  hammer  is  lifted  by  the  steam.  In  many  steam-hammers  of  modern 
construction  the  steam  is  admitted  to  both  sides  of  the  piston,  so  that  the  force  of  the  steam  upon 
the  upper  side  acts  to  increase  the  force  of  the  blow,  the  latter  being  modified  by  regulating  the 
pressure  of  the  steam  above  the  piston,  and  for  very  light  blows  by  throttling  the  exhaust-steam  be- 
low it,  as  well  as  regulating  the  stroke  of  the  hammer. 

A  double  upright  steam-hammer,  by  William  Sellers  &  Co.,  is  shown  in  Fig.  2285.     The  essential 

peculiarities  in  the  design  of  this  hammer  consist  in  making  the  hammer  one  long  bar  of  wrought- 
iron,  having  the  piston  welded  to  and  forming  part  thereof,  and  guiding  this  bar  by  the  top  and 
bottom  cylinder-heads  only,  thus  doing  away  with  the  usual  side-guides  in  the  hammer-frame,  and 
leaving  the  entire  space  below  the  cylinder  free  for  the  use  of  the  workman  in  handling  his  work, 
while  the  hammer-head  and  die  are  claimed  to  be  guided  more  efficiently  than  in  any  other  system, 
and  the  frames  to  be  subjected  to  less  strain. 

An  improvement  in  the  manner  of  attaching  the  die  to  the  bar  consists  in  employing  a  crimped 
steel  key,  which  holds  the  die  with  an  elastic  pressure,  and  operates  to  prevent  the  bending  or  the 
fracture  of  the  bar.  Another  improvement  consists  in  obtaining  the  motion  to  work  the  steam-valve 
from  two  diametrically  opposite  grooves,  operating  a  brass  yoke  whose  line  of  vibration  is  through 
the  central  axis  of  the  bar,  which  obviates  the  tendency  to  rotate  the  bar  existing  when  a  diagonal 
groove  is  employed  in  the  upper  end  of  the  bar.  By  a  modification  of  the  ports  in  the  steam-chest 
enabling  the  employment  of  a  supplemental  valve,  the  exhaust  may  be  throttled  below  without  im- 
peding the  free  exhaust  above  the  piston.  This  enables  the  hammer  to  strike  quick,  light  blows  for 
finishing ;  in  other  words,  the  hammer  can  go  up  as  quickly,  but  in  coming  down  its  force  may  be 
gauged  by  the  steam-cushion  upon  which  it  descends,  which  steam,  thus  condensed  in  bulk,  reex- 
pands  in  the  up-stroke,  to  the  manifest  economy  of  steam  used. 

The  Tliirty-Ton  Steam-Hammer. — Fig.  2286  represents  a  30-ton  steam-hammer,  constructed  by 
Messrs.  Thwaites  &  Carbutt,  of  Bradford,  England,  for  use  at  the  works  of  Sir  William  Armstrong 
&  Co.  at  Elswick.  The  main  standards,  it  will  be  seen,  are  cast  of  two  parts  each,  firmly  bolted  to- 
gether ;  they  are  circular  in  section,  taper  slightly,  and  are  inclined  toward  one  another.  They  are 
25  feet  high,  and  as  they  have  a  clear  span  at  the  floor-line  of  19  feet  10  inches,  there  is  ample 
space  for  the  manipulation  of  the  forgings.  The  guides,  which  are  cast  separately,  are  attached  to 
the  standards  in  a  firm,  unyielding  manner.     The  entablature  on  which  the  cylinder  rests  at  the  same 


time  connects  the  two  standards  to  which  it  is  bolted  and  wedged.  By  this  arrangement  and  sub- 
division into  several  parts  too  ponderous  castings  arc  avoided,  while  at  the  same  time  the  rigidity  of 
the  structure,  which  must  be  great  in  view  of  the  violence  and  frequency  of  shocks,  is  not  impaired. 
The  steam-cylinder,  permitting  a  12-foot  stroke,  is  4  feet  in  diameter;  it  is  placed  upon  the  entabla- 
ture, making  the  entire  height  of  the  hammer  42  feet  9  inches.  The  piston-rod  is  very  massive  and 
strong ;  it  is  firmly  keyed  to  the  30-ton  tup,  which  glides  in  slots  of  the  guides  by  means  of  a  pro- 
jection. An  attendant  on  the  platform  operates  the  valves  through  the  agency  of  rods  and  levers 
within  his  reach.  The  hammer  is,  according  to  Prof.  S.  Jordan,  served  by  two  20-  and  two  40-ton 
cranes,  each  of  which  is  furnished  with  three  hydraulic  motions  according  to  Armstrong's  system. 
The  heating  is  done  in  four  Siemens  gas  furnaces.  The  frame,  while  it  is  strong,  and  possesses  the 
advantage  of  affording  ample  space,  is  built  up  of  a  reasonable  amount  of  metal.  The  piston-rod 
may  appear  excessively  heavy  while  the  tup  is  proportionately  light;  this,  however,  is  a  distribution 
of  materia]  which  has  many  claims  to  consideration. 

The  Creusot  Eighty-Ton  Steam-Hammer. — The  largest  steam-hammer  in  existence  (1879)  is  that 
constructed  by  the  Messrs.  Schneider  at  the  famous  factory  of  Creusot,  France,  and  represented  in 
one  of  the  full-page  plates.  The  largest  hammers  previously  built  were  the  51-ton  hammer  at  the 
Perm  steel  works  (Russia),  the  50-ton  hammer  at  the  Alexandrovski  steel  works,  near  St.  Peters- 
burg, and  the  50-ton  hammer  at  Messrs.  Krupp's  works  at  Essen;  while  after  these  come  the  35-ton 
hammer  at  Woolwich  Arsenal,  and  the  30-ton  hammer  at  Sir  W.  G.  Armstrong  &  Co.'s  works  at 
Elswick,  England. 

In  Messrs.  Schneiders'  large  hammer  the  moving  mass  weighs  80,000  kilogrammes,  or  about  7SJ 
English  tons,  while  the  maximum  fall  is  5  metres,  or  about  10  feet  5  inches.  The  hammer  is  single- 
acting,  and  is  worked  with  steam  at  70  lbs.  pressure,  while  the  diameter  of  the  steam-cylinder  is 
74.8  inches.     The  other  principal  dimensions  arc  as  follows : 

Feet.  In.  , 

Diameter  of  piston-rod 1     2.2    Width  of  bed-plate 

Diameter    of    steam-admission    valve  Height  of  standards 

(Cornish) 1     1.4    Length  of  cylinder 

Diameter  of  exhaust-valve  (Cornish). . .  1  6.1    Total  height  from  bottom  of  base-plate 

Width  of  tup  between  guides 6     2.8        to  top  of  cylinder 

Width  between  legsof  hammer-frame..  24  7.3  \  Height  of  anvil-block 
Clear  height  under  lower  cross-stay  of 

framing 10  0 

Length  of  bed-plate 41  4 

Depth  of  masonry  below  anvil-block . 

Sui  lace  of  base  of  anvil-block 

Surface  of  top  of  anvil-block 















355  sq.ft. 



The  framing  of  the  hammer  consists  of  a  pair  of  inclined  legs  of  rectangular  box-section,  having 
the  guides  for  the  tup  bolted  to  their  inner  sides,  these  legs  being  connected  at  two  points  (namely, 
at  the  top  and  bottom  of  the  guide-)  by  massive  wrought-iron  plate  cross-stays,  while  at  the  top  they 
are  bolted  to  a  deep  casting  which  forms  the  base  of  the  cylinder.  Each  leg  is  cast  in  two  pieces 
bolted  together  by  external  flanges.  The  cylinder  is  also  made  in  two  pieces  bolted  together  at  the 
middle  of  its  length.  Each  leg  of  the  frame  is  forked, at  its  lower  end,  so  as  not  only  to  give  greater 
stability,  but  also  to  afford  access  to  the  anvil  from  the  Bides. 

In  constructing  the  anvil-block  for  the  large  hammer,  Messrs.  Schneider  wisely  departed  from  the 
practice  of  making  the  block  in  one  enormous  casting.  Instead  of  this,  they  made  the  block  in  six 
layers,  each  (except  the  top  one,  which  is  in  a  single  piece)  consisting  of  two  castings.  The  layers 
increase  in  thickness  as  they  diminish  in  area  from  the  base  upward,  and  the  castings  composing 
them  are  so  shaped  that  each  layer  is  firmly  interlocked  with  those  above  and  below  it,  the  line  of 
division  of  the  two  parts  of  one"  layer  being  at  right  angles  to  the  division  line  in  the  next  layer 
above,  and  so  on.  The  anvil-block  rests  upon  layers  of  oak  timber  making  up  a  thickness  c>f  about 
3  feet,  this  timber  again  resting  on  a  bed  of  masonry  in  cement  over  13  feet  thick,  which  bears 
directly  on  the  rock  below.  This  bed  of  masonry  extends  not  only  under  the  anvil-block,  but  under 
the  whole  area  occupied  by  the  hammer,  it  being  carried  up  around  the  anvil-block  to  support  the 
hammer  itself,  and  the  space  between  the  masonry  and  the  anvil-block  being  packed  with  oak  timber. 
It  follows  from  the  mode  of  construction  adopted  that  in  the  event  of  anything  going  wrong  with 
these  foundations,  it  would  be  quite  possible  to  lift  the  anvil-block  piece  by  piece,  and  to  make  the 
damage  good  ;  whereas,  if  the  block  had  been  cast  in  one  piece,  any  settlement,  if  it  did  take  place, 
would  be  very  difficult  to  deal  with. 

The  weights  of  the  various  parts  of  the  hammer  are  as  follows : 

D  Tons. 

Tup  with  piston  and  rod 80 

Cylinder 22 

Entablature 30 

Legs  of  hammer-frame  with  guides 250 

Wrought-iron  cross-stays 25 

Foundation-plate 90 

Valves,  valve-gear,  and  miscellaneous 35 

Total  weight  of  structure  above  ground 532 

Anvil  and  anvil-block 750 

Total 1,282 

To  serve  this  magnificent  hammer,  four  cranes  have  been  erected,  three  of  them  being  capable  of 
lifting  100  tons  each,  while  the  fourth  can  deal  with  a  load  of  160  tons.     They  are  all  of  the  revolv- 

HANGER.  97 

ing  post  class,  with  jibs  formed  of  curved  box-girders,  the  part  of  each  crane  below  the  ground  line 
being  also  a  box-girder  of  rectangular  section  tapering  from  the  ground  level  to  the  bottom.  The 
weight  of  each  crane  with  its  load  is  carried  by  a  ring  of  live  rollers  at  the  ground  level,  the  bottom 
of  the  crane-post  having  a  gudgeon  taking  lateral  stress  only.  The  foundation-plates  of  the  cranes 
are  connected  to  the  foundation-plate  of  the  hammer  as  well  as  to  the  masonry,  and  the  whole  work 
has  been  carried  out  so  as  to  make  a  thoroughly  sound  job.  Each  crane  has  a  maximum  radius  of 
30  feet  8  inches,  the  chain  carrying  the  ingots  passing  over  pulleys  on  a  traveling  carriage,  which 
can  be  racked  in  and  out  on  rails  on  the  top  of  the  jib.  The  height  from  the  floor  level  to  the  top 
of  these  rails  is  29  feet  6  inches,  while  from  the  floor  level  to  the  bottom  pivot  is  27  feet  6  inches. 
The  total  weight  of  each  100-ton  crane  is  110  tons,  while  the  160-ton  crane  weighs  140  tons.  Each 
crane  is  actuated  by  a  steam-engine  fixed  to  it,  this  engine  having  a  pair  of  cylinders  10.24  inches  in 
diameter  with  11.8  inches  stroke,  the  speed  at  which  these  engines  are  run  being  250  revolutions 
per  minute.  The  engines  work  not  only  the  lifting,  swinging,  and  racking  in  and  out  motions,  but 
also  serve  to  turn  over  the  forging  which  is  under  manipulation.  This  operation  is  effected  as  fol- 
lows :  The  forging  rests  as  usual  in  a  loop  or  bridle  of  massive  chain,  this  loop  passing  over  a  pulley 
mounted  on  a  frame  to  which  the  crane-chain  is  attached.  This  frame  also  carries  worm-gear  through 
which,  and  an  intermediate  wheel  and  pinion,  the  pulley  carrying  the  bridle-chain  can  be  rotated. 
The  worm  of  this  gear  is  coupled  by  a  shaft  with  two  universal  joints  to  a  short  shaft  on  the  crane- 
frame,  and  this  shaft  again  by  a  vertical  shaft  and  bevel-gear  is  connected  to  the  crank-shaft  of  the 
engine.  The  use  of  the  connecting-shaft  with  two  universal  joints  of  course  allows  the  forging  to  be 
raised  and  lowered  without  interfering  with  the  connection  between  the  engine  and  the  bridle-gear. 

The  furnaces  used  in  connection  with  the  80-ton  hammer  are  four  in  number,  and  they  are  of  the 
Siemens  regenerative  type.  The  heating  chamber  of  each  furnace  is  14  feet  1  inch  long  by  11  feet 
2  inches  wide,  and  8  feet  6  inches  high  in  the  centre,  the  crown  being  arched  in  both  directions.  The 
doors  of  these  mammoth  furnaces  are  raised  and  lowered  by  chains  led  down  to  horizontal  hydraulic 
cylinders  disposed  below  the  floor-line.  In  each  of  these  furnaces  the  regenerators  arc  as  usual 
below  the  bed,  the  regenerators  of  each  furnace  being  built  in  a  circular  pit,  which  also  contains  the 
hydraulic  gear  just  mentioned,  and  the  reversing  valves  for  gas  and  air.  The  part  of  this  pit  in 
front  of  the  furnace  is  bridged  over  by  massive  wrought-iron  girders  carrying  rails,  in  which  a  charge 
can  be  run  to  or  from  the  latter.  The  furnaces  are  supplied  with  gas  from  four  groups  of  nine 
generators  each,  which  also  furnish  gas  to  the  other  Siemens  furnaces  in  this  department.  The  80- 
ton  hammer  with  its  accessories  is  contained  in  a  building  of  which  the  frame  is  solely  of  iron.  This 
building  is  164  feet  long  by  114  feet  9  inches  wide,  and  55  feet  9  inches  high  to  the  springing  of  the 
roof.  To  the  ridge  of  the  roof  the  height  is  83  feet  8  inches,  and  to  the  top  of  the  lantern  which  the 
roof  carries  92  feet  7  inches.  The  building  is  spanned  by  girders  carrying  two  20-ton  crabs,  which 
serve  for  handling  parts  of  the  hammer  for  repairs,  etc.  (See  Engineering,  xxvi.,  28;  also  Annates 
Industriettes,  1S78.) 

HANGER.  A  device  for  supporting  shafting  from  overhead  or  from  the  side.  When  old-fash- 
ioned large  couplings  were  used  to  connect  shafting,  hangers  of  the  forms  shown  in  Figs.  2287  and 
2288  were  used.  The  modern  adjustable  coupling  obviates  the  necessity  of  spreading  the  hanger- 
legs  apart,  and  admits  of  the 

weight  of  the  appliance  being  2287.  2288. 

materially  decreased.  The  bear-    "  rrrL- 

ings  shown  in  these  figures  are 
also  disadvantageous  and  prac- 
tically obsolete.  That  exhibhed 
in  Fig.  2287  has  brass  bushings 
held  in  place  by  an  iron  cap  se- 
cured by  bolts.  In  Fig.  2288 
the  cap  is  dispensed  with,  and 
the  top  brass  is  fastened  only 
by  a  pin. 

For  very  heavy  head-shafts, 
the  ordinary  forms  of  hanger 

are  not  sufficiently  rigid  to  stand  the  lateral  strain  of  the  driving-belts,  and  it  is  therefore  generally 
the  custom  to  use  inverted  pillow-blocks  bolted  to  enough  timbers  to  bring  the  distance  of  the  drop 
equal  to  that  of  the  rest  of  the  line.  This  has  the  advantage  that  the  head-shaft  and  its  pulleys 
may  be  hoisted  directly  into  place  and  secured,  but  has  the  disadvantage  that  it  is  impossible  to 
remove  the  top  box  for  any  purpose  without  supporting  the  shaft  by  ropes  or  blocking  or  in  some 
such  way.  It  is  open  to  the  further  objection  that  it  possesses  no  vertical  adjustment.  To  obviate 
these  defects,  Messrs.  William  Sellers  &  Co.  have  designed  a  special  head-shaft  hanger,  Fig.  2289. 
The  cap,  supported  by  T-head  bolts,  is  removable  like  that  of  a  pillow-block ;  but  as  the  box  is  sup- 
ported by  screw-plungers,  it  not  only  has  a  vertical  adjustment,  but  like  a  hanger  will  permit  the 
top  box  to  be  removed  without  altering  the  alignment. 

Fig.  2290  represents  a  sectional  view  of  a  ball-and-socket  hanger.  The  two  half  boxes  b  and  c  are 
provided  with  turned  spherical  surfaces,  which  fit  into  corresponding  concave  surfaces  in  two  plungers 
d  and  e.  These  plungers  work  with  a  coarse  thread  in  two  boxes  a  a,  in  the  frame  of  the  hamrer, 
and  are  secured  from  turning  by  two  set-screws.  The  plungers  offer  a  vertical  adjustment,  while  the 
ball  and  socket  enable  the  boxes  to  adjust  themselves  to  the  shaft.  The  top  box  has  oil-holes  in  the 
centre  and  sides  of  the  ball,  and  oil  may  be  fed  from  an  oiler  placed  on  the  top  plunger  d.  Two 
recesses,  covered  by  loose  cast-iron  caps,  are  also  provided  to  contain  a  mixture  of  oil  and  tallow  that 
will  act  as  a  reserve  to  be  used  if  the  box  should  begin  to  heat ;  while  an  oil-dish  or  drip-pan  / 
catches  the  oil  that  drips  from  the  ends  of  the  boxes,  which  arc  provided  with  suitable  internal 










orooves  to  distribute  the  oil.  The  vertical  adjustment  afforded  by  this  style  of  bearings  is  one  of 
their  most  important  qualities,  and  one  that  cheapens  the  erection  of  shafting  and  facilitates  its 
realignment.  It  becomes  necessary  only  to  put  up  the  hangers  with  the  centres  of  the  boxes  in  the 
same°  vertical  plane,  and  any  adjustment  up  or  down  in  that  plane  may  be  readily  accomplished  by 
the  plungers.  .  .  . 

Ball-and-socket  bearings  are  made  of  different  bores  to  suit  the  commercial  sizes  ot  shafts,  and 
of  various  forms  to  suit  different  circumstances.  Thus  we  have  tint-hungers,  Fig.  2291,  which  are  of 
various  "  drops  "  or  distances  from  the  foot  (under  side  of  beam)  to  the  centre  of  the  box,  ordinarily 
from  8  to  30  or  36  inches.  In  ordering,  it  is  customary  to  mention  both  diameter  of  shaft  and  drop  ; 
as,  "a  2-inch  hanger,  10-inch  drop,"  or  "a  3-inch  hanger,  16  inch  drop." 

For  countershafts,  hangers  are  made  with  ball-and-socket  boxes,  but  without  vertical  adjustment, 
such  as  those  in  Figs.  2292  and  2293,  both  with  and  without  an  arm  to  carry  a  belt-shifting  bar.  For 
attachments  to  posts  or  walls,  post-hangers,  Fig.  2294,  are  made.  These  are  often  provided  with 
concave  feet  to  fit  cast-iron  columns  of  different  diameters.  C.  S.,  Jr. 

HARDENING.     See  Tempering  and  Hardening  of  Metals. 

HARNESS.     See  Looms. 

HARROW.     See  Agricultural  Machinery. 

HARVESTER.     See  Agricultural  Machinery. 

HAT-MAKING  MACHINERY.  The  manufacture  of  felt  hats  in  the  United  States  has  gradually 
become  divided  into  two  independent  branches — the  production  of  fur  hats,  made  from  the  fur  of  the 
gray  or  white  rabbit  or  hare,  known  in  the  trade  as  cony  or  Russian  fur,  and  of  wool  hats,  made 
from  different  kinds  of  wool.  Very  few  hats  are  manufactured  from  a  mixture  of  fur  and  wool,  or 
with  bodies  of  wool  covered  with  fur.  Although  the  methods  of  making  fur  and  wool  hats  are  ap- 
parently similar,  yet  the  machinery  employed  differs  so  materially  that  both  branches  of  the  trade 
are  rarely  conducted  in  the  same  establishment. 

Manufacture  of  Fur  Hats. 

There  are  various  ways  of  preparing  fur  for  felting.  Hare-skins  are  split  open  and  rubbed  with 
a  rough  knife-blade  to  remove  bits  of  adherent  fleshy  matter.  They  are  afterward  dampened  on  the 
pelt  side  and  pressed  together  pelt  to  pelt.  Rabbit-skins  are  treated  in  a  similar  manner,  except  that 
the  long  hairs  are  pulled  instead  of  being  clipped.     They  are  thus  made  ready  for  cutting. 

Cutting  is  accomplished  in  a  machine  having  a  rapidly-revolving  cylinder,  in  the  periphery  of 
which  three  or  more  knives  are  obliquely  set,  and  which  rotates  in  close  proximity  to  a  stationary 
bed-knife.  The  skin,  resting  upon  the  bed-knife,  is  divided  into  narrow  strips,  and  is  then  cut  away 
from  the  pelt,  which  is  thus  left  in  a  continuous  sheet.  The  fur  is  carried  by  an  endless  apron  to  a 
workman,  who  separates  it  into  various  grades  and  packs  it  in  bundles. 

Beaver  and  nutria  skins  require  more  care  in  their  handling  than  do  rabbit  or  hare  skins.  They 
are  loaded  with  fat,  which  must  be  removed  by  soap  and  water,  and  they  are  subsequently  treated 
with  a  dilute  solution  of  nitric  acid.  This  process  also  assists  the  felting  properties.  Skins  that 
have  been  thus  treated  are  said  to  be  "  carroted."  Thorough  drying  should  follow.  Hair  is  some- 
times prepared  in  a  solution  of  quicksilver  and  urine.  All  furs  are  more  or  less  mixed  with  long 
hair,  and  for  the  removal  of  this  the  fur-blowing  machine  is  employed. 

The  Fur-blowing  Machine  is  represented  in  Fig.  2295.  The  material  is  spread  upon  a  feeding 
apron  A,  and  by  means  of  two  rollers  B  is  presented  to  a  rapidly-rotating  toothed  cylinder  C.  The 
motion  of  this  cylinder  creates  an  air-current,  which  carries  the  lighter  particles  of  the  fur  upward 


into  a  chamber  which  is  closed  by  a  fine  wire  screen,  through  which  the  air  escapes,  carrying  the 
finer  particles  of  dust  with  it.  The  hair  and  coarse  particles  fall  upon  a  wire  screen,  which  is 
vibrated  by  a  cam  E,  and  thence  pass  upon  an  apron,  which  delivers  them  under  the  feed-apron. 
Another  feed-apron  forms  the  bottom  of  the  chamber  into  which  the  fur  passes ;  and  as  the  fur  set- 
tles on  this  apron  it  is  conducted  to  a  second  pair  of  feed-rollers,  which  carry  it  to  another  picker- 
cylinder,  where  the  operation  already  described  is  repeated. 

Most  fur-blowing  machines  contain  from  5  to  8  picker-cylinders,  the  fur  being  delivered  in  an 
endless  sliver  to  the  last  pair  of  rollers.  Hair  and  impurities  which  pass  through  the  screen  are  col- 
lected. Fur  which  does  not  pass  through  is  carried  back  by  an  apron  and  subjected  again  to  the 
action  of  the  machine.     This  operation  is  continued  until  the  quantity  of  hair  is  reduced  as  much  as 



is  possible.  In  forming  the  hat-body  various  kinds  of  fur  are  mixed  in  an  apparatus  which  contains 
a  picker-cylinder,  whereby  the  fur  is  loosened  and  thrown  into  a  closed  room,  or  into  a  machine 
similar  to  that  above  described,  by  which  it  is  delivered  in  a  continuous  bat.  The  fur  thus  prepared 
IS  weighed  and  separated  into  portions,  each  of  which  is  sufficient  to  form  one  hat-body. 

The  Forming  Machine. — The  apparatus  generally  in  use  is  that  invented  by  H.  A.  Wells  in  1846, 
and  since  greatly  modified  and  improved  by  Taylor,  Burr,  and  others.  In  the  Wells  machine  the  fur 
is  conducted  to  a  forming  cone  by  an  adjustable  trunk,  while  in  other  machines,  such  as  that  devised 
by  Gill  and  Taylor,  it  is  thrown  into  a  case  which  surrounds  the  former-cone,  and  is  conducted  to 
the  cone  by  an  air-blast  from  a  blower  beneath.  Fig.  2296  represents  a  Wells  machine  of  late  con- 
struction. An  apron  and  two  small  feed-rollers  deliver  the  fur  to  a  rotating  picker-cylinder.  The 
air-current  caused  by  the  latter  carries  the  fur  to  the  mouth  of  the  trunk.  The  size  of  the  aperture 
is  adjustable  to  correspond  to  that  of  the  cone  used.  The  cone  is  made  of  perforated  Bheet-copper, 
and  is  placed  upon  a  revolving  table,  in  the  centre  of  which  is  an  opening  communicating  with  an 


exhaust-fan,  by  means  of  which  an  air-current  is  drawn  in  through  the  perforations,  so  that  the  fur 
is  thus  caused  to  be  deposited  over  the  surface  of  the  cone.  This  process  continues  until  all  the  fur 
set  apart  for  one  hat-body  is  thus  deposited.     Over  the  material  a  wet  cloth  is  wrapped,  and  over 

this  again  a  tin  cover  is  placed,  when  the  whole  is  removed  and  dipped  in  hot  water  in  order  to  give 
the  felt  a  sufficient  consistence  to  allow  it  to  be  removed  from  the  cone. 

Hardening  the  felt,  which  follows,  is  done  by  placing  six  or  more  of  the  felt-cones  formed  as  above 
one  upon  the  other,  Wrapping  them  in  a  wet  blanket,  and  rolling  them  back  and  forth  by  hand  on  a 
smooth  board. 

Sizing. — This  name  is  given  to  the  manipulations  by  which  the  felt  is  reduced  to  the  proper  size 
for  hat-making.  Up  to  a  very  recent  date  (1879)  this  work  was  done,  and  is  still  largely  performed, 
entirely  by  hand.  Three  or  four  hat-bodies  are  dipped  into  boiling  water  (sometimes  slightly  acidu- 
lated), and  then  are  wrapped  in  cloths,  making  a  bundle  some  4  inches  in  diameter.  The  bundle  is 
rolled  to  and  fro  on  an  inclined  plank,  and  the  pressure  of  the  hands  is  carefully  graduated  to  the 
consistence  of  the  hat-body.  After  being  rolled  for  a  short  time,  the  bodies  are  separated  and  placed 
together  again  in  different  position,  so  as  to  prevent  their  sticking  together.  As  the  process  con- 
tinues, the  roll  is  made  tighter  and  the  pressure  increased,  until  the  body  has  attained  the  desired  size 
The  felt  is  then  "  pinned  out  " — that  is,  smoothed  and  tightened  by  pressure  with  a  rolling-pin  and 
frequent  dipping  in  hot  water. 

The  machine-  used  for  this  purpose  are  the  invention  of  Mr.  R.  Eickemeyer  of  Yonkers,  N.  Y.,  and 
are  modifications  of  the  fulling-mills  used  in  the  manufacture  of  wool  hats.  The  bodies  after  leaving 
the  former  are  placed  first  in  pusher-crank  mills.  These  mills  have  a  single  pendulum-beater  sus- 
pended from  the  top  of  an  iron  frame  and  operated  by  a  bell-crank,  which  receives  motion  from  a 
crank  on  the  main  shaft.  The  wrist-pin  on  the  bell-crank  is  adjustable,  so  that  the  force  with  which 
the  bodies  are  pushed  against  the  curved  part  of  the  bed  may  be  graduated.  This  operation  is  con- 
tinued until  the  felting  has  progressed  far  enough  to  allow  the  hats  to  be  placed  in  the  fulling-mill 
proper,  Fig.  2297.  This  machine  has  a  single  beater  pivoted  to  the  front  of  the  frame.  On  the 
opposite  end  is  a  horizontal  driving-shaft,  which  makes  120  revolutions  per  minute.  In  the  middle 
is  a  gripping-roller,  against  which  a  lifting-board  attached  to  the  end  of  the  beater-handles  is  at 
regular  intervals  pressed  by  another  gripping-roller  journaled  in  a  swinging  frame.  A  stepped  pul- 
ley on  the  driving-shaft  communicates  motion  to  a  second  shaft,  on  which  are  cams  which  actuate 
the  swinging  frame.  The  speed  of  this  shaft  determines  the  period  of  lift  and  drop  of  the  beater. 
The  amount  of  lift  and  drop  can  be  regulated  from  50  lifts  8  inches  high  per  minute  to  38  lifts  20 
inches  high  per  minute.  The  fullin^-bed  is  formed  of  two  pieces  of  metal  hinged  at  the  base,  the 
lower  portion  being  perforated  to  allow  entrance  of  steam  during  the  fulling  process.  The  front  por- 
tion is  hinged  to  the  stationary  part,  and  is  connected  by  links  to  a  rock-shaft  and  lever  which  en- 
ables the  operator  to  increase  resistance  to  the  movement  of  the  hat-bodies.  When  the  mill  is  first 
set  in  operation,  the  beater  is  adjusted  to  a  fall  of  about  8  inches,  and  is  run  at  the  rate  of  50  blows 
per  minute,  care  being  taken  that  the  position  of  the  hats  is  constantly  changed.  As  the  fulling 
progresses  the  front  is  lowered,  and  the  fall  of  the  beater  increased  and  its  rapidity  reduced,  until  at 
the  end  the  fall  becomes  fully  20  inches  and  the  blows  38  per  minute. 



After  being  fulled,  the  hat-bodies  are  passed  while  hot  through  a  pinning-out  machine,  Fig.  2298, 
in  order  to  tighten  the  felt  and  smooth  them.  This  apparatus  consists  of  two  pairs  of  rollers,  one 
pair  having  rigid  bearings,  the  other  being  pivoted  in  weighted  levers.  The  upper  pair  of  rollers  is 
slightly  the  larger  in  diameter, 
and  all  revolve  at  the  same 
uniform  speed.  Through 
these  the  body,  after  being 
dipped  in  hot  water,  is  passed. 
The  diameter  of  the  lower 
rollers  being  less,  however, 
than  that  of  the  upper  ones, 
the  hat-body  is  drawn  out 
between  them,  and  the  felt 
at  the  same  time  is  rendered 
compact  and  free  from  wrin- 

Sizing  Machines. — Numer- 
ous attempts  have  been  made 
to  construct  sizing  machines 
to  supplant  the  hand-sizing 
process.  The  machines  op- 
erate upon  a  limited  number 
of  hats,  rolled  in  a  cloth  and 
kept  in  motion  by  rollers 
which  have  a  vibrating  move- 
ment. In  one  class  of  ma- 
chines these  rollers  are  irreg- 
ularly ribbed  to  press  succes- 
sively upon  different  parts  of 
the  hat.  The  machine  de- 
vised by  Mr.  J.  S.  Taylor  of 
Danbury,  Conn.,  in  1853,  has 
four  rollers,  so  journaled  in 
their  frames  that  their  axes 
are  inclined  to  the  centre  of 
the  hat-roll,  and  one  pair  of 
rollers  has  a  vibrating  motion 
in  addition  to  its  movement 

of  rotation.  In  the  machine  devised  by  Mr.  J.  W.  Blackham  of  Brooklyn,  N.  Y.,  a  number  of  slowly- 
revolving  rollers  form  a  bed  over  which  is  placed  a  yielding  cover,  having  a  vibrating  motion  in  a 
direction  at  right  angles  to  the  axes  of  the  rollers.     The  hat-rolls  are  passed  between  cover  and  bed 

several  times.  It  has  not  been  found 
profitable  to  begin  sizing  the  body 
by  machinery  as  soon  as  it  leaves 
the  former,  and  hence  the  present 
practice  is  to  size  the  body  by  hand 
until  it  is  within  an  inch  of  its  de- 
sired dimensions,  and  then  to  com- 
plete the  work  in  the  sizing  machine 
— or,  as  it  is  then  termed,  the  sec- 
ond-sizing machine. 

A  machine  adapted  to  this  second 
sizing  has  been  devised  by  Mr.  J. 
Yero  of  Dewsbury,  England,  and 
improved  by  Kirk,  Shelmerdine,  and 
Froygate,  of  Stockport,  England. 
The  improved  apparatus  has  four 
rollers  driven  all  in  the  same  direc- 
tion by  gearing.  The  lower  pair  of 
rollers  is  journaled  in  the  station- 
ary frame,  while  the  upper  pair  is 
journaled  in  a  swinging  frame,  which 
can  be  lifted  up  whenever  the  hat- 
roll  is  to  be  inserted  or  removed. 
The  working  surface  of  the  rollers 
is  formed  of  elliptical  rings,  made 
of  India-rubber,  and  placed  so  as  to 
overlap  each  other.  Generally,  two 
rolls  of  hats  are  kept  in  operation, 
one  roll  being  acted  upon  while  the  positions  of  the  hats  in  the  other  are  being  changed. 

Fig.  2299  represents  a  machine  of  this  class.  Two  beaters  act  upon  the  ends  of  the  hat-roll. 
Four  cubical  pressers  are  provided,  so  arranged  that  the  hat-roll  is  pressed  at  each  quarter  revolution 
of  the  pressers.     These  are  journaled  upon  two  swinging  frames,  which  are  so  connected  by  links  to 



levers  in  the  rock-shaft  that,  while  balancing  each  other,  the  pressers  can  be  separated  to  take  out  or 
insert  a  hat-roll,  or  be  brought  together  by  a  weight  on  the  hand-lever.  The  pressers  arc  actuated 
from  the  main  shaft,  two  cams  on  which  operate  the  beaters.  On  each  beater  is  a  projection,  to 
which  an  adjustable  spring  is  attached  in  order  to  graduate  the  blow  upon  the  hat-rim.  Devices  are 
provided  whereby  the  spring  may  be  held  at  any  tension  suitable  to  the  condition  of  the  bodies.     By 

a  gradual  increase  of  the  weight  which  presses  the  rollers  or  pressers  together,  and  a  similar  increase 
of  the  t « -ii - i< >■  1  of  the  heater-spring,  the  action  of  tin-  machine  is  adjusted  as  the  felting  progresses. 

Some  grades  of  hats  are  sheared  before  the  sizing  or  felting  is  finished,  in  order  to  remove  long 
hairs.  Eickemeyer's  machine  for  shaving  hats  is  represented  in  Fig.  2800.  The  hat  is  placed  on  a 
padded  board  of  the  same  shape  as  the  body,  and  a  knife  is  caused  to  vibrate  rapidly  over  the  sur- 
face of  the  latter  while  the  feeding  mechanism  draws  the  hat  along,  slowly  rotating  it.     The  best 

speed  iif  the  knife  is  from  600 
2300.  to  660  strokes  per  minute,  and 

from  3  to  6  dozen  hats  can  be 
shaved  without  change  of  knife. 
Stiffening  /In  hat-body  is  the 
next  process.  Alter  drying,  the 
felt  is  dipped  in  an  alkaline 
solution  or  one  of  shellac. 
Stronger  solutions  are  used  for 
the    brim    than    Cor    the   crown 

of  the  hat.     Passing  between 

weighted  rollers  follows,  the 
surplus  stiffening  material  fall- 
ing back  into  the  tank  to  which 
the  rollers  are  attached.  The 
body  is  folded  and  rolled  sev- 
eral times,  until  the  stiffening 
solution  is  evenly  distributed. 
The  brim  is  stiffened  afterward, 
and  rolled  in  similar  manner. 
Some  manufacturers  prefer  to 
apply  all  the  stiffening  after 
the  body  has  been  blocked  and 
colored;  while  others  only  par- 
tially apply  stiffening  in  ad- 
vance, reserving  the  completion 
of  the  process  until  after  block- 
ing.    After  stiffening,  the  body  is  steamed,  and  is  then  ready  for  the  initial  shaping  processes. 

Stretching  and  Blocking. — The  hat-body  has  now  reached  a  point  where  it  begins  to  assume  a 
semblance  of  the  completed  article  through  the  development  of  the  tip,  side-crown,  and  brim. 
Many  attempts  have  been  male  to  accomplish  shaping  by  machinery.  The  first  United  State-  patent 
was  granted  to  Mr.  D.  Beard  of  Guilford,  N.  C,  in  1816,  for  a  machine  for  stretching  hat-crowns. 
Other  devices  have  subsequently  been  invented  and  come  into  limited  use ;  but  it  appears  that  the 
practical  difficulties  were  not  successfully  overcome  until  the  invention  in  1865  of  the  hat-stretching 
machines  of  Mr.  R.  Eickemeyer.  In  previous  apparatus  the  effort  was  to  stretch  the  hat-body  from 
the  centre;  in  the  Eickemeyer  machines  the  body  is  stretched  over  a  ribbed  and  recessed  former, 



and  is  thus  drawn  out  radially,  the 
centre  being  widened  at  those  parts 
which  form  the  crown  and  brim  of 
the  hat.  The  former  is  secured 
to  a  sliding  spindle,  which  is  actu- 
ated by  a  treadle  and  link.  Directly 
over  and  in  line  with  the  spindle  are 
suspended  adjustable  stretching- 
fingers.  When  these  are  brought 
down  by  means  of  a  hand-wheel 
connected  with  their  spindle,  they 
are  closed  in  around  the  hat-body, 
and  their  pressure  is  increased. 
To  suit  hats  of  varying  diameters, 
a  star  is  fastened  upon  the  spin- 
dle. The  hats  to  be  stretched  are 
first  soaked  to  render  the  felt  pli- 
able, then  placed  upon  the  star, 
and  forced  down  upon  the  stretch- 
ing-fingers. This  operation  is  re- 
peated five  or  six  times.  At  each 
motion  the  height  to  which  the 
body  is  lifted  and  turned,  to  bring 
the  stretcher  in  contact  with  all 
parts,  is  increased.  Usually  two 
hat-bodies  are  stretched  at  a  time, 
both  being  turned  inside  out  so 
as  to  protect  them  against  injury 
through  contact  with  the  stretch- 

The  brim-stretcher  is  represented 
in  Fig.  2301.  This  consists  of  a 
series  of  expansible  ribs  mounted 
upon  a  sliding  spindle  in  the  cen- 
tre  of   the   machine.      Connected 

tre    oi    ine    macniue.      v/uimci-n-u 

with  the  spindle  is  a  system  of  links  and  levers  operated  by  the  treadle,  by  which  means  the  spindle 
is  caused  to  rise,  and  so  bring  the  ribs  into  working  position.  Above  the  ribs  is  a  hat-block  which 
can  be  adjusted  to  any  height.     The  stretching-fingers  are  so  arranged  as  to  be  automatically 

reciprocated  toward  or  from  the  centre  of  the 
machine.  The  outer  ends  of  the  fingers  are 
connected  by  short  links  to  a  ring  fastened  to 
two  upright  sliding  bars,  which  have  their  bear- 
ings in  the  side  frames  of  the  machine,  and  re- 
ceive motion  from  the  crank  on  the  main  shaft. 
The  crank-shaft  makes  from  300  to  350  revo- 
lutions per  minute,  producing  the  same  number 
of  vibrations  of  the  stretching-fingers.  The 
hat-body  is  adjusted  upon  the  block,  the  treadle 
is  depressed  to  its  full  extent,  and  the  hand- 
lever  on  the  right  of  the  machine  is  raised. 
The  ribs  upon  which  rests  that  portion  of  the 
body  which  is  to  form  the  brim  are  spread  out 
between  the  vibrating  fingers.  After  10  or  15 
stretches  are  made  by  the  fingers,  the  block  is 
lowered  sufficiently  to  turn  the  hat  upon  it,  so 
as  to  bring  the  fingers  upon  that  portion  which 
previously  rested  on  the  ribs,  and  the  operation 
is  repeated.  From  30  to  40  vibrations  of  the 
fingers  are  usually  sufficient  to  stretch  the  brim 
to  its  full  extent. 

These  machines  differ  considerably  in  con 
struction,  according  as  they  are  applied  to  dif- 
ferent uses.  Fig.  2302  represents  the  Eicke- 
meyer  fur-tip  stretcher.  In  this  the  fingers  are 
mounted  on  a  spindle  which  has  its  bearing  in 
line  with  the  sliding  spindle  which  supports  the 
star.  To  this  spindle  a  short  walking-beam, 
which  also  communicates  with  the  crank-shaft, 
is  hinged.  Each  revolution  of  the  main  shaft 
thus  causes  vertical  movement  of  the  spindle, 
and  also  of  the  stretching-fingers.  In  practice 
the  best  results  are  obtained  at  from  100  to 
150  revolutions  of  the  main  shaft. 



2303.  Blocking.— Fig.  2303  rep- 

resents the  Eickeineyer  hand 
hat-blocking  machine,  which 
operates  as  follows :  A  hat 
previously  stretched  on  the 
tip,  side-crown,  and  brim  is 
clamped  on  the  outer  edge 
and  expanded  to  the  desired 
size.  Thirty-six  clamping- 
tongs  are  pivoted  to  the  lop 
plate,  in  an  oval  line  around 
the  block,  and  these  are  at- 
tached to  the  foot-lever  so 
as  to  more  outward  from  the 
centre  when  the  lever  is  de- 
pressed. Each  one  of  the 
clamping-tongs  is  also  con- 
aected  to  a  clamping-lever, 
so  that  all  may  be  simulta- 
neously drawn  upon  the  brim 
placed  between  them.  An 
adjustable  block  composed 
of  48  pieces,  which  are  also 
spread  out   from  the  a 

by  one  of  the  levers  shown, 
i-  mounted  on  a  sliding  spin- 
dle, aid  can  be  raised  or 
lowered.  To  form  the  band 
of  the  hat,  a  ring  of  the  ex- 
act size  and  shape  is  sus- 
pended from  the  hand-lever, 
which  is  pivoted  horizontally 
to  brackets.  Adjusting-screws  are  provided  for  regulating  the  height  and  diameter  of  the  crown, 
and  "  brim-tongs  "  govern  the  exact  width  to  which  the  brim  is  to  be  drawn  out. 

The  operation  ol  blocking  is  performed  as  follows:  The  upper  or  banding  lever  having  been 
raised,  the  block  is  con- 
tracted and  lowered,  and 
the  clamping-tongs  are 
closed  in.  One  or  two 
hats,  having  been  thor- 
oughly heated  in  hot 
water,  are  placed  upon 
the  block,  the  brim  rest- 
ingupon  the  heads  of  the 
clamping-  tongs,  which 
are  now  expanded  suffi- 
ciently to  allow  the  edge 
of  the  brim  to  slip  dofl  □ 
upon  the  lower  jaws. 
The  tongs  are  then  made 
to  approach  the  hat  un- 
til the  edge  of  the  brim 
touches  the  upper  jaws 
all  around,  when  the 
clamping-lever  is  pulled 
forward,  and  all  the  up- 
per jaws  are  closed  upon 
the  brim,  which  i-  thus 
firmly  held  and  slowly 
expanded  to  full  size. 
The  hat-block  is  in  the 
mean  time  raised  and 
the  banding-lever  low- 
ered ;  and  after  the  block 
has  been  expanded,  the 
workman  gives  the  band- 
ing-lever rapid  up-aud- 
down  motion  to  form 
the  band.  The  hat  is 
then  cooled  in  place  by 
cold  water,  when  it  sets 

in  proper  shape.    From  50  to  SO  dozen  hats  can  be  thus  blocked  per  day 
and  colored,  and  usually  blocked  a  second  time, 

The  hats  are  next  washed 
They  are  then  ready  for  the  pouncing  machine. 



Pouncing  Machines. — Various  forms  of  these  machines  are  used.  In  one  of  the  simplest  the  hat 
is  subjected  to  the  scraping  action  of  a  rapidly  revolving  cutting-cylinder.  In  another,  the  abrading 
material  is  sand-  or  emery-paper  secured 

to  vibrating  arms.     In  a  third,  the  hat  is  -30"'- 

fastened  to  a  block  which  turns  to  and 
fro  around  its  centre,  while  the  rubbing 
material  is  held  up  to  its  surface.  The 
first-mentioned  machine  is  best  adapted 
for  coarser  grades  of  hats,  the  others  be- 
ing preferable  for  hats  of  fine  quality. 
Fig.  2304  represents  the  Universal  poun- 
cing machine,  by  means  of  which  a  hat- 
body  which  has  not  been  blocked  is 
pounced.  A  conical  roller  covered  with 
fine  sand-  or  emery-paper  is  secured  to  a 
horizontal  shaft,  and  makes  from  2,000 
to  2,500  revolutions  per  minute.  Con- 
ical feed-rollers,  one  of  which  in  Fig. 
2304  is  shown  as  pressing  upon  the  hat- 
body  while  the  other  is  in  the  inside  of 
the  latter,  have  their  bearings  in  two 
frames  hinged  to  the  main  frame.  These 
may  be  adjusted  nearer  to  or  farther 
from  the  cutting-roller,  as  well  as  longi- 
tudinally in  the  direction  of  the  axis  of 
the  cutting-roller  shaft,  so  that  hats  of 
any  shape  may  be  operated  upon.  The 
relative  positions  of  the  feed-rollers  may 
also  be  varied  so  as  to  press  harder  at 
any  desired  point.  The  hat  is  supported 
on  a  horn  hinged  to  the  main  frame,  and 
is  kept  in  working  contact  by  the  attend 
ant  pressing  upon  the  treadle  shown.  A 
small  exhaust-blower  serves  to  remove  the 
material  abraded  or  cut  off.  The  machine 
just  described  is  chiefly  used  for  poun- 
cing brims,  the  side-crown  and  tip  of  the 
hat  being  operated  upon  in  another  ap- 

Fig.  2305  represents  the  Labiaux  crown- 
pouncing  machine.    Two  spindles  are  pro- 
vided, one  of  which  has  a  hat-block  secured  on  its  inner  end,  while  to  the  other  the  cutting-cylinder 
is  fastened.     These  have  their  bearings  in  lathe-heads  mounted  centrally  upon  and  pivoted  to  short 

columns,  which  can  be  turned  around 
2306.  by  suitable  handles.    Both  spindles 

SFjmTi  slide  longitudinally  in  their  bear- 

ings, and  in  the  flanged  pulleys 
which  give  motion  to  them.  A  fast 
motion  is  given  to  the  cutting-spin- 
dle, and  a  comparatively  slow  one 
to  that  which  carries  the  block.  Af- 
ter the  hat  has  been  tightly  drawn 
upon  the  block,  the  machine  is  set 
in  motion,  and  the  spindle  of  the 
block  is  turned  on  its  column  until 
the  tip  of  the  hat  touches  the  cut- 
ting-roller ;  the  block  is  then  turned 
slowly  back  while  the  cutting-roller 
is  pressed  against  the  surface  of  the 
hat,  and  is  slowly  passed  over  the 
square  side-crown  and  tip,  often 
two  or  three  times  to  produce  the 
:  necessary  smooth  finish.  This  ma- 
chine is  in  some  establishments  used 
only  for  rough  work,  fine  pouncing 
being  completed  on  the  apparatus 
illustrated  in  Fig.  2306,  and  known 
as  the  Rosekranz  brim-machine. 

In  this  device  two  vibrating  rub- 
bing arms  are  pivoted  to  a  heavy 
frame,  and  actuated  in  opposite  di- 
rections from  an  upright  crank-shaft.     Each  arm  has  on  its  outer  end  a  plate  covered  with  sand-  or 
emery-paper.     The  upper  arm  is  attached  to  the  treadle  on  the  right  of  the  machine,  and  can  be 



raised  to  introduce  or  remove  the  brim  of  the  hat.  A  swinging  frame  contains  the  shafts  of  the  two 
conical  feed-rollers,  the  upper  one  of  which  is  raised  when  desired  by  the  treadle;  otherwise  the 
weight  shown  presses  it  upon  the  hat.  The  rollers  receive  motion  from  the  upright  shaft  in  front  of 
the  machine,  through  a  system  of  bevel-gear.  To  regulate  the  motion  of  the  hat  circumferentially, 
the  rollers  can  be  set  close  to  the  rubbing  plates,  or  for  wide  brims  they  may  be  moved  farther  away. 

Means  are  provided  for  holding  the 
treadle  down,  and  thus  keeping  the 
rubbing  surfaces  and  feed-rollers  apart, 
when  the  machine  is  in  motion  but  do- 
ing no  work.  The  feed-rollers,  first 
(.•rasping  the  brim,  give  it  a  slowly  ro- 
tating motion,  and  the  rubbing  plates 
when  closed  acl  against  both  sides  of 
it.  This  produces  a  smooth  and  even 

To  pounce  the  crown,  it  is  necessary 
to  place  the  hat  over  a  block.  A  ma- 
chine for  crown-pouncing  is  represent- 
ed in  Fig.  2307.  An  upright  spindle, 
which  has  its  bearing  in  the  frame,  com- 
municates with  the  sliding  head  by  two 
straps  uhich  are  fastened  to  o]  pi 
ends  of  a  cross-head,  and  also  are 
wrapped  in  opposite  directions  around 
tin'  spindle,  and  are  attached  one  near 
the  upper,  the  other  near  the  low  er  bear- 
ing of  the  latter.  The  cross-head  i-  con- 
nected by  rods  to  the  wrist-pin  on  the 
fly-wheel.  The  motion  imparted  to  the  cross-head  through  the  connecting  rod  i~  transmitted  through 
the  two  straps  to  the  spindle,  and  produces  two  revolutions  of  the  latter,  first  in  one  and  then  in  the 
other  direction,  to  each  turn  of  the  driving-shaft.  The  block  for  the  reception  "I  the  hat  is  secured 
upon  the  upper  end  of  the  spindle,  and  may  be  removed  by  means  of  the  small  hand-lever  shown. 
The  rubbing  material  is  held  against  the  crown  by  hand,  and  is  slowly  carried  all  over  the  surface. 


Finishing  Il/'s. — The  finishing  of  fur  hats  includes  the  final  blocking,  the  shaping,  ironing,  and 
smoothing.  Soft  hats  arc  first  drawn  over  a  block  of  the  desired  shape.  The  brim  is  then  flattened 
out,  and  while  damp  the  hat  is  ironed  all  over.  Rubbing  with  fine  sand-paper  follows,  and  then  sev- 
eral repetitions  of  the  wetting  and  ironing  for  fine  goods,  or  only  two  ironings  and  wettings  for 
inferior  grades.  To  give  the  hat  a  velvet  finish,  it  is  ironed  first,  then  carefully  rubbed  over  with  fine 
sand-  or  emery-paper,  and  finally  held  over  a  jet  of  steam  which  raises  the  nap.    It  is  afterward  singed. 



A  pressure  of  about 

Stiff  hats  are  differently  treated.  The  hat  is  first  steamed  on  a  block,  the  brim  flattened,  and  the 
surface  rubbed  with  emery-paper.  The  brim  is  then  cut  to  the  right  width,  and  the  binding  is  put 
on.  The  brim  is  next  to  be  curled,  and  for  this  purpose  it  is  placed  upon  a  convex  plate  heated  by 
steam.  This  softens  the  brim,  so  that  it  can  be  turned  over  toward  the  crown  and  ironed  down, 
forming  a  fold  or  roll  gradually  widen- 
ing from  the  front  and  rear  to  the  sides. 
The  brim  is  then  bent  to  any  shape  or 
curve,  according  to  the  prevailing  fash- 
ion. To  shape  a  stiff  felt  hat  properly 
is  the  most  difficult  part  of  its  manufac- 

Hydraulic  presses  have  of  late  been 
used  with  some  success  in  pressing  <titf 
hats.  The  hat  is  heated  in  an  oven  by 
steam,  and  is  pressed  either  in  a  cold 
mould  or  in  a  hot  one,  to  shape  the  crown 
and  flatten  the  brim.  In  one  machine  of 
this  kind,  the  hat  is  placed  in  a  mould 
and  an  India-rubber  cover  is  closed  over 
it.  This  cover  or  diaphragm  is  expand- 
ed and  pressed  against  the  hat  by  water 
forced  between  the  diaphragm  and  a  sta- 
tionary head  by  a  pump.  A  press  man- 
ufactured by  Mr.  George  Yule  of  New- 
ark, N.  J.,  is  represented  in  Fig.  2308. 
It  consists  of  a  heating  chamber  in  which 
the  hat  is  placed  upon  its  block.  The 
press-follower  is  driven  down  by  the  pis- 
ton of  the  hydraulic  cylinder,  and  is  balanced  by  the  counterweight  shown. 
300  lbs.  is  usually  applied. 

Ironing  Machines. — Fig.  2309  represents  an  improved  ironing  machine  which  operates  upon  all 
parts  of  the  hat.  Its  action  is  entirely  automatic,  one  operator  being  able  to  attend  to  two  or  more 
machines.  The  chief  improvements  embodied  consist  in  the  attachment  of  side-crown  and  tip  irons 
to  a  vibrating  arm,  to  enable  the  latter  to  iron  the  square  of  the  hat,  and  the  introduction  of  a  fast- 
running  ironing  disk  to  iron  the  under  brim.  The  hat,  secured  on  the  finishing  block,  is  placed  on 
an  upright  shaft  which  revolves  slowly.  Another  upright  spindle,  situated  about  10  inches  to  the 
right  of  the  first,  has  a  disk  fastened  to  its  upper  end,  which  is  heated  by  a  Bunsen  gas-burner.  This 
disk  revolves  about  four  times  as  fast  as  the  hat-block,  and  in  the  opposite  direction.  Its  flat  side, 
which  acts  as  an  iron  for  the  under  brim,  is  adjusted  level  with  the  under  side  of  the  hat.  A  trav- 
ersing motion  is  imparted  to  the  tip  and  side-crown  irons,  so  that  they  move  from  the  centre  of  the 
tip  and  side-crown  to  the  scpiare  of  the  hat.     The  device  for  ironing  the  upper  brim  is  suspended  in 

a  hinged  lever,  and  is  held 
by  a  weight  up  to  the  hat- 
block.  In  operation,  the 
upper  brim  iron  is  placed 
upon  the  brim  ;  and  as  the 
friction  of  the  latter  on  the 
iron  has  a  tendency  to  draw 
the  brim  along,  while  the 
fixed  upper  iron  retards 
this  motion  to  the  same  ex- 
tent, no  wrinkling  of  the 
material  is  produced.  The 
tip  and  side-crown  irons  are 
arranged  to  follow  the  ir- 
regular shape  of  the  block. 
The  traverse  motion  is  then 
started,  and  the  irons  move 
to  and  fro,  thus  completing 
the  smoothing  of  all  parts 
of  the  hat. 

When  sufficiently  ironed, 
the  hat  is  placed  in  a  poun- 
cing machine,  Fig.  2310, 
on  a  block  which  is  mount- 
ed on  an  eccentric  chuck, 
which  has  a  reciprocating 
as  well  as  a  rotary  motion. 
Rubbing  with  sand-  or  em- 
ery-paper follows,  and  then  another  ironing ;  and  finally,  if  a  velvet  finish  is  desired,  the  hat  is  singed. 
Manufacture  of  Wool  Hats. 

The  machinery  used  for  preparing  wool  for  hat-making  is  the  same  as  that  employed  in  its  pre- 
paration for  spinning.     (See  Wool  Machinery.)     The  former  used  for  making  the  hat-bodies  is 



placed  in  front  of  the  carding  machine,  and  the  sliver  is  wound  upon  a  double  cone,  making  two  hat- 
bodies  at  a  time.  These  are  divided  and  removed  from  the  cone  when  a  sufficient  quantity  of  mate- 
rial has  been  gathered.  The  wool-former  is  older  than  the  fur-former,  and  it  remains  substantially 
as  it  was  patented  by  Mr.  J.  Grant  in  1827,  all  modifications  tending  to  make  its  parts  more  adjust- 
able and  to  increase  their  durability.  The  machine  is  represented  in  Fig.  2311.  It  is  constructed  so 
as  to  be  easily  adjustable  to  suit  the  largest  size  of  man's  or  the  smallest  size  of  child's  hat.  Ar- 
rangements are  provided  whereby  an  equal  quantity  of  wool  is  wound  on  both  sides  of  the  former- 
cone.  The  speed  of  the  latter  is  regulated 
by  shifting  a  small  spur-wheel  on  the  coun- 
tershaft, which  has  its  bearing  in  a  swing- 
ing frame  on  the  side,  and  is  parallel  with  a 
scries  of  gear-wheels  of  varying  diameters 
keyed  upon  the  main  driving-shaft.  Anoth- 
er improvement  is  the  arrangement  of  a  stop- 
motion  to  arrest  the  movement  when  the 
former-cone  is  parallel  with  the  carding  ma- 
chine. When  a  large  quantity  of  wool  is  to 
be  wound  on  the  cone  to  form  a  heavy  brim, 
it  is  necessary  that  the  machine  should  Btop 
in  proper  position,  and  this  is  effected  by  the 
automatic  devices  provided. 

Hardening. — Fig.  2812  represents  a  double 
hardening  machine.  A  board  of  the  shape 
of  a  h&t-body  when  flattened  out  is  connect- 
ed with  an  adjustable  wrist-pin  on  the  fly- 
wheel. Steam-boxes  of  the  shape  of  the 
body  are  set  in  the  top  of  the   table,  and  arc 

perforated    lor   the   passage  of  steam.     A 
pice  of  cloth  is  inserted  in  the  body  to  scp- 
-",;>:_; .._  arate  the  Bides,  and  several  bodies  thus  pre- 

pared are  superposed.  The  engraving  shows 
one  of  the  boards  resting  upon  two  hat-bodies  and  held  down  by  a  post,  which  presses  it  upon  the 
bodies  with  sufficient  force  to  compress  them  to  a  thickness  of  about  a  quarter  of  an  inch.  The 
rapid  vibration  of  the  hardening  board  upon  the  hats  renders  the  material  sufficiently  tough  to  stand 

the  actii Ethe  fulling-mill.     After  one  side  has  thus  been  hardened,  the  bodies  are  removed  and 

refolded,  and  the  operation  is  repeated. 

TPulling, — The  first  operation  of  fulling  is  conducted  in  a  crank-mill  essentially  similar  to  that  de- 
scribed as  lor  fur  hats,  but  which  has  two  beaters  acting  in  opposite  directions  on  one  fulling-bcd. 
The    hats    are   here   fulled    with    fullers' 
soap.     Afterward  they  are  placed  in  the 
mill  represented  in  Fig.  2313.    Four  cast- 
iron  frames  fastened  upon  a  solid  foun- 
dation support  the  shafts  upon  which  tie 
hammers  are  pivoted,  and  also  the  full- 
ing-bed,  which   is  divided  into  two  com- 
partments.    The  hammers  are  lifted   by     . 
toes  on  the  two  large  gear-wheels,  one  of    ( 
which   is  shown  in   the  engraving.     The      ta 
capacity  of  these  mills  is  from  20  to  25 
dozen  hats  fulled  in  from  24  to  48  hours. 
The  hammers  are  lifted  in  succession  and 
drop  upon  the  goods,  which  are  slowly 
turned.     In  some  cases  steam  is  admitted 
into  the  mill.     After  fulling,  the  bodies 
are  washed  in  a  crank-mill,  and  are  then 
ready  to  be  stretched  and  blocked,  or  stiff- 
ened and  then  stretched  and  blocked,  as 
the  goods  may  require. 

Siretching  and  Blocking. — The  Eieke- 
meyer  tip-stretcher,  already  described  un- 
der fur  lint  manufacture,  is  largely  used 
for  this  purpose.  A  special  machine  has 
however  been  devised,  which  is  illustra- 
ted in  Fig.  2314.  This  apparatus  has  a 
former  of  peculiar  shape.    The  rib- which 

support  the  tip  are  connected,  and  the  stretching-fingers  are  formed  at  an  obtuse  angle  on  the  line 
where  they  come  in  contact  with  the  body.  Each  finger  is  hinged  at  its  middle  to  a  disk,  which  is  at- 
tached to  the  upright  cylinder  fitted  in  the  upper  cross-piece ;  and  on  its  outer  end  it  is  secured  to  a  ring 
which  is  held  by  set-screws  to  the  two  sliding  rods  in  the  side  frame.  The  ring  is  actuated  through 
connecting-rods  by  the  crank-shaft,  and  thus  caused  to  make  an  up-and-down  movement  at  each 
revolution  of  the  latter.  The  walking-beam  on  top  of  the  machine  is  attached  on  its  left  end  by  a 
link  to  the  cross-piece,  at  its  middle  to  the  cross-piece  which  carries  the  sliding  fingers,  and  at  its 
right-hand  end  to  the  vibrating  ring.     This  connection  gives  to  the  disk  an  up-and-down  travel  of 



about  half  the  length  of  that  of 
the  ring.  The  fingers,  as  already 
stated,  being  hinged  to  the  disk 
and  ring,  thus  have  at  their  lower 
extremities  a  movement  to  and 
from  the  centre  of  the  hat,  while 
they  remain  stationary  at  their  point 
of  meeting  above.  The  effect  of 
this  is  that  the  hat-tip  is  stretched 
peripherally  only,  and  not  radial- 
ly in  addition,  as  is  done  on  some 
other  machines.  Each  one  of  the 
vibrating  fingers  works  in  a  recess, 
into  which  a  portion  of  the  felt  is 
drawn  at  each  vibration ;  and  as 
the  body  is  supported  all  around, 
a  portion  of  the  crown  as  well  as 
the  tip  is  drawn  out.  From  100 
to  120  dozen  hats  per  day  can  be 
stretched  on  this  machine. 

From  the  tip-stretcher,  the  hat- 
body  is  taken  to  the  power  brim- 
stretcher,  and  then  while  hot  is 
placed  on  the  blocking  machine. 
This  apparatus,  represented  in  Fig. 
2315,  differs  chiefly  from  other  ma- 
chines of  its  class  in  the  operation 
of  the  bandintr-ring.  To  make  a 
sharp  edge  at  the  junction  of  the 
brim  and  side-crown  is  the  special 
object  of  blocking ;  and  although 
the  crown  is  also  shaped,  that  part 
of  the  work  is  already  done  on  the 
stretcher.  The  framing  of  the  ma- 
chine and  the  driving  mechanism  are  substantially  the  same  as  in  the  power  tip-stretcher  just  de- 
scribed ;  but  in  place  of  a  former,  the  brim  is  supported  by  an  annular  plate,  which  is  recessed  in 


the  centre  to  receive  a  hat-block  of 
the  desired  size  and  shape.  Anoth- 
er plate  is  suspended  by  rois  from 
the  upper  cross-piece.  When  the 
treadle  is  depressed,  and  the  sliding 
spindle  with  the  brim-plate  raised, 
the  hat-brim  is  clamped  and  held 
fast  between  the  two  plates.  The 
driving-shaft  gives  a  vibratory  mo- 
tion to  the  side-rods,  to  the  upper 
end  of  which  a  cross-head  with  the 
banding-ring  is  attached.  The  band- 
ing-ring thus  has  a  rapid  vertical  mo- 
tion. When  the  hat  is  placed  on  the 
block,  it  is  clamped.  The  block  is 
then  raised  by  a  hand-lever  until  its 
under  side  is  in  the  same  plane  as 
the  hat-brim,  where  it  is  secured  by 
hook-latches.  The  operator,  while 
keeping  his  weight  on  the  treadle, 
now  removes  the  hat  previously 
blocked  while  the  band  is  formed  in 
the  hat  in  the  machine.  The  treadle 
is  then  lowered  enough  to  take  off 
the  hat  and  block,  and  is  allowed  to 
descend  to  its  lowest  position  to  re- 
lease the  sliding  head  upon  which 
the  block  rests,  and  permit  it  to  drop 
below  the  surface  of  the  brim-plate, 
where  it  is  held  until  the  hat  is  re- 
moved by  the  hook-latches  already 
mentioned.  A  set  of  machines,  name- 
ly, tip  and  brim  stretchers  and  block- 
er, working  in  succession,  will  block 
from  100  to  120  dozen  hats  daily. 

The  coloring,  stiffening,  and  wash- 
ing processes  are  the  same  as  already 



described  for  fur  hats.  The  Eickemeyer  pouncing  machine  noted  in  the  same  connection  is  also 
largely  used.  Two  machines  are  however  required,  a  right-hand  and  a  left-hand  machine,  in  order 
to  produce  a  nap  in  the  same  direction  on  both  sides  of  the  brim.  This  is  not  requisite  in  fur-hat 
making,  owing  to  the  softness  of  the  material.     It  is  now  necessary  to  remove  all  the  fine  dust  from 

the  surface  of  the  hat,  and  for  this  purpose 
2316.  the  same  machine  is  used.     The  cutting-roller 

i.-  replaced  by  a  cylindrical  brush. 

The  treatment  of  wool  hats  in  the  finishing 
room  differs  from  that  of  fur  hats,  in  BO  fai 
that  the  hat-body  is  always  softened  by  a 
steam-jel  when  it  is  to  be  drawn  on  the  fin- 
ishing-block or  shaping-flange. 

Finishing. — Two  methods  are  chiefly  em- 
ployed to  give  the  wool  hat  its  proper  shape 
and  finish.  Hats  with  brims  very  much  cur\  ed, 
and  turned  <>n  the  upper  edge  toward  the  crown, 
are  first  steamed,  and  the  i-t]<sv  of  the  brim  is 
seemed  to  the  periphery  of  a  mould  of  suitable 
form.  A  second  steaming  follows,  and  the 
block  is  forced  into  the  crown  by  means  of  a 
hver  until  its  under  side  is  even  with  the 
brim,  which  is  thus  drawn  tightly  over  the 
mould,  alter  cooling,  the  edge  of  the  brim 
i<  cut,  and  the  hat  is  then  while  on  the  block 
removed  from  the  mould.  The  block  is  se- 
cured upon  a  rapidly  revolving  lathe-head, 
when  the  crown  is  first  retouched  with  sand- 
paper, and  finished  by  rubbing  with  a  piece  of 
felt  by  hand.  This  last  is  termed  "ragging." 
Hats  with  flat  brims  arc  first  steamed  on 
the  finishing-block,  and  the  band  secured  by  a  cord.  The  brim  is  flattened  and  ironed,  and  the  hat 
is  placed  in  the  finishing  lathe,  rubbed  with  sand-paper,  and  ragged.  Before  the  hal  is  trimmed, the 
crown  (and,  if  flat,  the  brim)  is  pressed  in  a  hot  mould  or  on  a  hot  plate.  Fig.  2316  represents  a 
hand-lever  press  used  for  this  purpose.  The  hat  is  placed  in  a  brass  mould,  and  upon  a  hollow  iron 
bed-plate  heated  by  steam.  By  means  of  the  cros.-heads  shown,  the  pressure  upon  the  rubber  dia- 
phragm inside  of  the  block  is  regulated.  Usually  three  of  these  presses  are  placed  in  a  row,  and  by 
the  time  a  hat  is  placed  in  the  last  of  the  series,  that  in  the  first  is  pressed,  and  thus  the  work  of 
pressing  is  continuously  kept  up. 

In  trimming  hats,  the  principal  machine  to  be  noted  is  a  sewing-machine  which  sews  in  the  sweat- 
leathers      It  is  very  ingeniously  constructed,  bo  that  brims  of  any  shape  or  curve  may  be  introduced. 
The  large  majority  of  the  machines  described  in  this  article  are  the  invention  of  Mr.  R.  Eickemeyer 
of  Yonkevs,  X.  V.,  to  whom  we  are  indebted  for  the  facts  embodied  in  their  description.     G.  II.  B. 
HAT-FORK.    See  Agricultural  Machinery. 
HAY-LoADER.    See  AGRiciLTtitAi.  Machinery. 
HAY-RAKE.     See  Agricultural  Machinery. 
HEAD-FORMING  MACHINE.     See  Barrel  Machinery. 
HEADING.     See  Carpentry. 
HEARTH.    Sec  Furnaces. 

HEATER,  FEED-WATER.     See  Boilers,  Steam. 
HEATER,  FIREPLACE.     See  Stoves  and  Heating  Furnaces. 

Steam-Heating. — The  Holly  System  of  Hod', ,ng  Cili<s. — The  most  extensive  application  of  steam 
to  warming  purposes  which  has  been  made  has  been  introduced  in  Lockport,  N.  Y.,  by  the  Holly 
Steam  Combination  Company.  Through  the  winter  of  1877-78  about  three  miles  of  underground 
pipe  were  laid,  supplying  steam  to  forty  large  dwellings,  a  school-building,  and  a  hall,  and  also  to 
two  engines,  one  of  them  nearly  half  a  mile  distant  from  the  boiler-house.  The  following  description 
and  data  obtained  by  test  have  been  contributed  by  the  inventor  of  the  system,  Mr.  Birdsill  Holly: 

"  It  was  at  first  claimed  that  a  district  half  a  mile  square  could  be  warmed  with  boilers  located  at 
one  central  point ;  but  f requent  tests  along  the  first  line  of  underground  pipe  soon  began  to  show 
that  a  very  much  larger  district  could  thus  be  heated.  At  the  farther  end  of  1,600  feet  of  3-inch 
pipe  the  water  from  condensed  steam  was  trapped  out  and  weighed  for  12  hours;  the  result  showed 
15.6  cubic  feet,  or  31.2  cubic  feet  for  24  hours.  Then,  on  the  basis  of  10  to  1  for  evaporation,  we 
have  31.2  x  62.5  (1  cubic  foot)  =  1,950  lbs.  water  -4-  10  =  195  lbs.  of  coal,  costing  30  cents  per  day. 
The  second  test  was  to  ascertain  the  quantity  of  steam  that  would  pass  through  the  pipe  with  a  pres- 
sure in  the  boiler  of  25  lbs.  The  pressure  at  the  farther  end  of  the  pipe  was  drawn  down  from  25 
lbs.  to  10  lbs.  (a  good  working  pressure)  by  letting  the  steam  escape  into  the  air.  The  coal  was  then 
carefully  weighed  for  several  hours,  showing  a  consumption  of  400  lbs.  of  coal  per  hour,  or  9,600 
lbs.  per  24  hours,  which  would  evaporate  96,000  lbs.  of  water  into  2,688,000  cubic  feet  of  steam,  at 
the  pressure  of  the  atmosphere.  Then,  allowing  each  consumer  on  the  line  12,000  cubic  feet  of 
steam  at  the  above  pressure,  which  will  warm  10,000  cubic  feet  of  space  in  blocks  for  16  hours  a 
day,  we  have  2,688,000  -=-  12,000  =  224  consumers  to  share  the  loss  of  30  cents  per  day.  Then  the 
loss  in  the  large  mains  is  to  be  added,  making  the  total  loss  by  condensation,  in  a  district  of  24,000 


consumers,  40  cents  per  year  for  each  consumer  with  a  pressure  in  the  mains  of  25  lbs.  A  test  made 
in  the  winter  with  the  same  amount  of  surface,  but  with  32  lbs.  instead  of  25  in  the  mains,  showed 
a  loss  of  10  per  cent,  more ;  but  in  no  case  can  the  loss  be  more  than  60  cents  per  year  for  each  con- 
sumer, even  with  a  pressure  of  50  lbs.  in  the  mains.  Consumers  in  a  district  of  dwellings  more 
scattered  and  exposed  on  all  sides,  requiring  about  50  per  cent,  more  steam,  calling  for  larger  and 
longer  mains,  are  charged  from  $1  to  §1.50  per  year  to  overcome  the  loss  by  condensation.  Then, 
on  Ihe  other  hand,  suppose  this  same  district  of  exposed  dwellings  were  to  be  warmed  by  steam  in 
the  old  way — that  is,  with  a  small  boiler  in  each  dwelling.  The  loss  by  condensation  due  to  the 
steam-boiler  alone  (as  per  tests  made  by  the  writer)  is  from  40  to  60  lbs.  of  coal  per  day  to  hold  10 
lbs.  of  steam  and  not  draw  any  out.  Tests  were  also  made  on  evaporation  with  the  same  boilers  as 
they  were  used  with  radiators,  which  showed  but  4  lbs.  of  water  with  1  lb.  of  coal.  The  cause  of 
this  low  duty  is  the  slow  combustion,  as  a  boiler  large  enough  to  warm  all  the  rooms  in  a  dwelling 
in  the  coldest  weather  is  entirely  too  large  to  warm  two  or  three  rooms  in  mild  weather.  If  but  10 
lbs.  of  coal  is  required  to  do  the  warming,  it  will  still  require  from  40  to  60  lbs.  to  hold  steam  on 
the  boiler.  It  is  considered  reasonable  to  charge  50  lbs.  of  coal  per  day,  or  5  tons  per  year,  costing 
$20,  and  the  interest  on  a  steam-boiler,  fixtures,  and  setting  up,  say  $21,  making  $41  per  year. 

"  The  street-mains  in  Lockport  are  common  gas-pipe,  covered  with  asbestos,  woolen  felt,  then  hair- 
cloth three-fourths  of  an  inch  thick,  and  protected  with  strong  manilla  paper,  then  put  inside  of  wood 
pipe  4  inches  thick  outside  of  the  iron  pipe ;  then  all  is  covered  with  roofing  felt.  The  trench  is 
about  3  feet  deep  to  the  top  of  the  tile,  and  is  above  all  other  pipes.  The  service-pipes  are  not 
taken  direct  from  the  wrought-iron  pipes,  but  from  stationary  cast-iron  junction  boxes,  which  form 
the  slip-joints,  and  receive  the  ends  of  the  service-pipes.  Each  box  is  surrounded  by  a  wall  of  brick 
or  stone,  with  a  loose  cover,  so  as  to  be  accessible.  The  above-quoted  tests  on  condensation  were 
made  with  3-inch  pipe.  The  per  cent,  of  loss  by  condensation  decreases  as  the  pipe  is  enlarged. 
The  per  cent,  of  loss  for  a  3-inch  pipe  was  9  in  400;  for  a  6-inch,  18  in  2,400;  for  a  12-inch,  36  in 
14,400 ;  for  24-inch  pipe,  72  in  80,000. 

"Steam  may  be  carried  a  distance  of  10  miles  in  large  pipes,  and  then  be  used  for  both  power  and 
warming ;  but  this  will  never  be  called  for,  as  all  the  consumers  in  a  district  of  4  square  miles  can 
be  reached  with  mains  less  than  2  miles  long. 

"  Cost  of  the  System. — The  estimated  cost  of  warming  a  district  one  mile  square  in  the  city  of  New 
York  or  Chicago  is  as  follows  :  1.  As  to  the  amount  of  space  to  be  warmed,  it  is  assumed  that  at 
least  two  full  stories,  say  100  feet  deep  by  15  feet  high,  on  each  side  of  the  street,  will  require  steam, 
as  in  many  blocks  and  hotels  it  will  be  used  in  the  third  and  fourth  stories,  and  more  or  less  in  the 
basements.  Then  we  have  100  x  15  =  1,500  x  2  =  3,000  x  2  =  6,000  cubic  feet  of  space  for  each 
lineal  foot  of  street,  including  both  sides.  Then  take  say  one  mile  of  street,  5,2S0  feet,  deduct  25 
per  cent,  for  cross  streets  and  walls  between  stories,  and  we  have  about  4,000  feet  left.  Then 
4,000  x  6,000  =  24,000,000  cubic  feet  of  space  to  be  warmed  for  each  mile  of  street.  Then  24,000,- 
000  x  10  =  240,000,000  cubic  feet  for  the  square  mile,  not  including  the  cross  streets,  which  would 
add  something  more.  Then,  according  to  tests  made  at  Lockport  during  the  winter,  one  cubic  foot 
of  steam  at  the  pressure  of  the  atmosphere  will  warm  one  cubic  foot  of  space  in  stores,  offices,  and 
dwellings  in  blocks  for  16  hours,  being  about  the  average  time  per  day  that  steam  is  used.  Then 
240,000,000  cubic  feet  of  steam  is  required  per  day.  Each  cubic  foot  of  steam  was  a  cubic  inch  of 
water.  Now  we  have  240,000,000  cubic  inches  of  water  to  evaporate  each  day ;  and  as  1  lb.  of  coal 
will  evaporate  10  lbs.  of  water,  and  make  280  cubic  feet  of  steam,  we  have  240,000,000  -e-  280  = 
857,142.8  h-  2,000  (1  ton)  =  428.5  tons  x  $3  per  ton  =  $1,276.50  per  day.  Then  $1,276.50  x  200 
days  =  $255,300  per  year  of  200  days.  Allowing  10,000  cubic  feet  of  space  for  each  consumer,  we 
have  240,000,000 -v-  10,000  =  24,000  consumers.  Then  $255,300  -f-  24,000  =  $11.05  per  year  each 
for  coal  alone. 

"  Total  Cost  of  Works  to  supply  24,000  Consumers. 

12  miles  of  6-inch  pipe,  at  $3.50  per  foot $221,000 

50  boilers  and  fixtures  set  complete 150,000 

Boiler-house  and  lot 75,000 

Engineering  and  incidentals 50,000 

Total $496,000 

Running  Expenses. 

Coal,  wood,  and  other  expenses 300,000 

Fireman  and  other  help 10,000 

Office  expenses 10,000 

Collecting 8,000 

Taxes  and  incidentals 50,000 

40  per  cent,  on  capital  stock 198,400 

Total $576,400 

24,000  consumers  at  $24 $576,000 

24,000  consumers  at  $40 960,000 

"  Cost  of  radiators  and  other  fixtures  for  24,000  consumers,  at  $200  each,  $4,800,000.  If  this  work 
is  done  by  the  company,  allowing  10  per  cent,  profit  on  the  work,  this  would  amount  to  $480,000." 

Steam-Heating  of  Buildings. — The  method  of  warming  buildings  by  steam  depends  on  the  rapid 
condensation  of  steam  into  water  when  admitted  into  any  vessel  which  is  not  so  hot  as  itself.  At 
the  moment  of  condensation,  the  latent  heat  of  the  steam  is  given  out  to  the  vessel  containing  it,  and 
this  diffuses  the  heat  into  the  surrounding  space. 



Steam  is  applied  for  heating  in  two  ways:  either  by  coils  of  pipes  or  combined  metallic  sheets 
(radiators)  set  up  in  the  various  apartments,  which  warm  by  direct  radiation  ;  or  by  systems  of  pipes 
over  which  air  is  made  to  pass,  and,  being  heated,  is  sent  through  the  building  by  flues.  This  last  is 
called  the  indirect  radiation  system.  The  choice  of  direct  or  indirect  radiation  will  depend  on  the 
construction  of  the  building  and  on  the  purposes  for  which  it  is  intended.  Direct  radiation  is  the 
most  economical,  for  the  reason  that  radiant  heat  is  utilized,  while  in  indirect  radiation  it  is  partially 
lost.  The  temperature  in  pipes  should  never  be  below  212°;  otherwise  the  steam  rapidly  condenses 
to  water,  to  get  rid  of  which  the  pipes  must  be  inclined  so  that  the  water  may  easily  How  back  to  the 
boiler,  or  drip-pipes  communicating  with  the  bottom  of  the  radiators  and  feed-pipe  ;  the  pipes  should 
be  so  inclined  that  the  water  will  flow  in  the  same  direction  that  the  steam  does. 

Steam  possesses  an  advantage  over  hot  water  in  the  case  of  application  where  great  inequalities 
and  frequent  alterations  of  level  occur,  and  particularly  where  the  boiler  must  be  placed  higher  than 
the  places  to  be  heated.  The  original  cosl  of  steam  apparatus  is  somewhat  less  than  that  of  hot- 
water  apparatus. 

Designing  of  Steam  Apparatus. — To  proportion  a  boiler  for  a  given  steam-pressure,  see  Boilers. 
The  evaporating  power  should  be  30  per  cent,  larger  than  the  quantity  of  water  condensed  in  the 
pipes.  The  billowing  table  shows  proportions  of  pipes  when  the  pressure  of  steam  is  not  above  15 
lbs.  per  square  inch  (saturated  steam): 

Connecting-pipes  to  Coil*— Direct,  or  Indirect  Radiation. 

Coil  Surface. 

Diameter  of  Pipe. 

Sectiooal  Area. 

25  square  feet  or  le-s. 
•in            » 

160            "          " 

'j.            "          " 

\  inch. 

1    •• 
1  \  - 

2  inches. 

i'.  1 1  Bquare  inch. 
0.78      " 

1.22        "          " 

L.76      "        " 
3.14  square  inches. 

The  sectional  area  of  a  branch  pipe  must  equal   the  area  of  all  connection-pipes,  and  the  sectional 
area  of  a  main  pipe  must  equal  the  area  of  all  branch  pipes.     The  sectional  area  of  the  return-pipes 

from  a  coil  or  series  of  coils 
must  lie  one  size  less  than 
the  respective  flow-pipe  to  the 
coil.  Drip-pipes  should  con- 
nect with  all  risers  (vertical 
flow-pipes),  the  water  being 
taken  into  the  return-pipes  or 
boiler.  The  sectional  area  of 
main  pipes  should  bo  reduced 
as  soon  as  practicable.* 

Instead  of  unions  for  join- 
ing pipes,  a  coupling  is  com- 
monly employed  having  a 
right-  and  left-hand  thread 
which  fits  on  corresponding 
threads  formed  on  the  pipe 
ends.  Similarly,  where  two 
elbows  are  attached  to  one 
pipe,  one  elbow-thread  is 
right-  and  the  other  left- 
handed.  The  arrangement  has 
the  advantages  of  cheapness 
and  easy  repair. 

Arrangement  of  Pipes  in 
the  Mills  System  of  Steam- 
keating. — In  this  system,  the 
invention  of  Mr.  J.  H.  Mills, 
steam  under  pressure  from  the 
generator  or  boiler  is  conduct- 
ed directly  upward  through 
the  main  supply-pipe  until  it 
reaches  the  return-pipe,  down 
which  it  descends  until  it 
reaches  the  connecting-pipe 
of  eaeh  radiator  whose  valve 
is  open.  After  circulating 
through  the  same,  and  part- 
ing with  its  heat,  it  is  con- 
densed, and  the  resultant  water  flows  through  the  outlet  or  drip-pipe  into  the  return-pipe,  and  directly 
down  the  latter,  without  hindrance  or  check,  where  it  is  discharged  into  the  generator. 

*  From  "A  Manual  of  Heating  and  "Ventilation,"  by  F.  Schumann,  C.  E.,  New  York,  1  ~TT. 



The  general  arrangement  of  piping  will  be  understood  from  Fig.  2317.  The  supply-pipe  is  led  as 
shown  to  any  convenient  point  near  the  highest  radiator,  from  which  point  the  supply  becomes  also  the 
return,  to  which  the  radiators  are  connected  with  a  single  valve,  the  outlet  and  the  tee  being  above 
or  below  the  floor,  as  desired.  The  steam  entering  the  supply-pipe  expels  the  contained  air,  not  into 
the  rooms,  but  into  the  basement,  through  the  air-vent  provided,  establishing  at  once  a  circulation 
regardless  of  the  radiators,  which  if  open  go  immediately  to  work,  as  most  of  their  air  is  drawn  out 
by  the  descending  circulation  of  the  steam  and  water.  The  air  is  allowed  to  fall  out  of  the  pipes, 
instead  of  being  lifted  and 
forced  out ;  and  the  pipes  un- 
der this  arrangement  do  more 
efficient  work  as  soon  as  steam 
is  raised  and  as  long  as  it  re- 
mains. The  radiator  now  be- 
ing wanted,  it  is  necessary  to 
open  but  one  valve,  which  ad- 
mits the  steam  and  also  dis- 
charges the  water,  the  air  only 
of  the  radiator  being  dis- 
charged into  the  rooms. 

The  Albany  Steam  -  Trap, 
represented  in  Figs.  2318  and 
2319,  is  a  mechanical  device 
which  is  convertibly  either  a 
steam-trap  or  a  boiler-feeder.  As  a  steam-trap  it  returns  the  water  of  condensation  from  the 
heating  coils  or  pipes  to  the  boiler,  whether  the  same  are  above  or  below  the  water-level  in  the 
latter.  As  a  boiler-feeder  it  supplies  any  deficiency  of  water  in  the  generator.  It  consists  essen- 
tially of  a  hollow  globe,  supported  by  one  end  of  a  lever  and  counterbalanced  by  a  weight  at  the 
other.  The  topmost  pipe  is  connected  with  the  steam-space  of  the  boiler,  and  is  opened  and  closed 
to  the  globe  by  the  automatic  weighted  valve  seen  on  the  top  of  the  same.  The  larger  pipe  beneath 
supplies  the  globe  or  trap  with  the  condensed  water  from  the  heating  apparatus.  It  is  provided  with 
a  check-valve  opening  inward.     The  pipe  at  the  bottom  connects  the  globe  with  the  water-space  of 

the  boiler,  and  is  furnished  with  a  check-valve  opening  outward.  The  operation  is  as  follows :  When 
the  globe  becomes  filled  with  a  certain  amount  of  the  water  of  condensation,  it  overbalances  the 
weight  at  the  other  end  of  the  lever,  and  descends.  In  descending,  it  moves  the  mechanism  of  the 
steam-valve  sufficiently  to  shift  the  centre  of  gravity  of  the  attached  weight  beyond  its  supporting 
point,  which  allows  the  globe  to  fall  and  open  the  steam-valve.  The  steam-pressure  closes  the  check- 
valve  in  the  supply-pipe,  and  allows  the  water  in  the  trap  to 'flow  into  the  boiler  through  the  bottom 
pipe,  whose  check-valve  opens  to  let  it  pass.  When  the  globe  has  lost  sufficient  weight  through  the 
escape  of  the  water,  it  is  raised  again  by  the  weighted  lever,  and  the  steam-valve  is  shut  by  the 



operation  of  its  attendant  mechanism.  The  water  of  condensation  is  again  admitted  by  the  opening 
of  the  check-valve  in  the  supply-pipe,  and  the  operation  is  repeated  continuously.  The  steam-valve 
apparatus  is  so  nicely  adjusted  that  the  machine  cannot  by  any  possibility  rest  on  a  centre ;  the 

valve  must  always  be  fully  opened  or  closely 
232°-  shut.     An  air-valve   is  also   attached  to  the 

globe,  through  which  the  air  is  expelled. 

Fig.  2319  shows  the  trap  in  connection  with 
the  boiler  and  coils.  It  will  be  observed  that 
this  device  does  not  "trap"  off  the  water  into 
some  drain  to  be  wasted,  or  into  a  tank  from 
which  it  is  to  be  again  pumped  into  the  boil- 
er; but  it  takes  the  water  directly  from  the 
heating-coils,  whether  at  a  point  above  or  be- 
low the  boiler  is  of  no  consequence,  and  re- 
turns it  without  loss  to  the  boiler,  at  a  tem- 
perature of  over  200°,  effecting  thereby  alone 
a  Baving  in  the  cost  of  fuel,  besides  the  advan- 
tage of  keeping  the  boiler  fed  with  pure  water. 
There  is  also  an  advantage  in  the  fact  that 
this  trap,  like  the  heart  action  in  the  human 
body,  forces  and  keeps  up  a  continuous  circu- 
lation, occasioning  thereby  a  greater  radiation 
of  heat  from  a  given  surface. 

Construction  of  Radiators. — A  sectional  view 
of  Carr's  radiator  is  given  in  Fig,  2320.  This 
construction  is  the  most  approved,  inasmuch 
as  a  positive  circulation  of  steam  is  secured,  and  at  the  same  time  all  trouble  from  the  water  of  con- 
densation is  avoided.  It  will  be  observed  in  the  section  of  the  base,  thai  between  each  pair  of  the 
pipes  that  are  connected  at  the  top  there  are  depressions  in  the  bottom  of  the  base,  and  a  correspond- 
ing partition  extending  from  the  top  of  the  base  into  the  depressions.  When  the  steam  is  let  on,  the 
water  of  condensation  passes  along  the  bottom  of  the  base,  filling  those  depressions,  passing  under 
and  covering  the  bottom  of  the  partitions,  forming  a  water-seal,  and  thus  preventing  the  pa-sage  of 
the  steam.  The  steam  will  therefore  follow  the  course  of  the  arrows,  passing  up  the  first  pipe  and 
down  the  second  into  the  second  chamber;  there  meeting  with  the  resistance  of  the  water-seal,  it  will 
pass  up  the  third  pipe,  and  so  into  the  chamber,  and  so  through  any  number  of  pipes  to  the  discharge 
or  return  pipe  ;  and  as  there  is  no  other 
course  for  it  to  follow,  it  must  neces- 
sarily expel  the  air  and  heat  the  w'n  »le 
of  the  pipes,  while  the  water  of  con- 
densation will  fall  to  the  bottom  of  the 
base,  and  pass  off  under  the  partitions 
to  the  discharge-pipe. 

Warner's  System  of  Steam-Heating  by 
Direct  Radiation. — This  is  one  of  the 
simplest  systems  of  low-pressure  steam- 
heating  apparatus  which  possess  effi- 
cient means  for  self-regulation.  It  is 
hardly  necessary  to  point  out  that  where 
the  management  of  apparatus  of  this 
Kind  is,  as  must  be  the  case,  commonly 
left  to  inexperienced  persons,  automatic 
devices  for  confining  the  steam-pressure 
to  proper  limits,  and  governing  the  con- 
sumption of  fuel  and  supply  of  water, 
are  of  especial  importance.  The  boiler, 
Fig.  2321,  is  upright,  and  its  general 
construction  is  clear  from  the  engrav- 
ing. A  is  the  water-feeder,  B  the  ser- 
vice-pipe connected  with  the  water-pipes 
from  the  street  or  from  a  tank  in  the 
house.  This  water-feeder  is  composed 
of  a  cast-iron  chamber,  inclosing  a  lever, 
having  at  one  end  a  copper  float,  and  at 
the  other  a  valve  governing  the  flow  of 
water  into  the  boiler.  When  the  boiler 
requires  water,  the  valve  opens  and  al- 
lows it  to  flow  in.  When  it  has  received 
the  proper  quantity,  the  float  rises,  shuts 
the  valve,  and  stops  the  flow  of  water 
till  more  is  required.     The  water-feeder 

is  so  connected  with  the  boiler  that  it  is  not  affected  by  the  pressure  of  the  steam,  and  operates 
equally  whether  there  is  or  is  not  a  steam-pressure.  A  glar-s  gauge  on  the  side  of  the  water- 
feeder  indicates  the  exact  height  of  the  water  in  the  boiler,  and  gives  notice  if  from  any  cause 



the  supply  fails.  The  tube  D  is  a  hydrostatic  column  connected  with  the  bottom  of  the  boiler,  being 
in  effect  a  part  of  the  boiler  itself,  and  is  always  open  to  the  external  air.  Before  steam  is  gen- 
erated, the  water  in  the  tube  and  boiler  is  on  a  level ;  but  when  the  fire  is  kindled  and  more  steam 
is  generated  than  is  required  to  fill  the  steam-chamber  and  the  radiators  that  are  open  to  receive  it, 
a  pressure  is  created  upon  the  surface  of  the  water  in  the  boiler,  and  this  counterbalancing  column 
rises.  When  the  steam  accumulates  to  the  pressure  of  one  pound  to  the  square  inch,  the  column 
will  stand  26  inches  above  the  level  of  the  wa- 
ter in  the  boiler,  according  to  a  well-known  law  2322. 
of  nature.  This  simple  process  is  employed  to 
regulate  the  draught  to  the  fire,  as  well  as  the 
accumulation  and  pressure  of  steam.  To  this 
column  are  attached  three  bowls — E,  F,  G — with 
elastic  heads  connecting  with  levers,  as  seen  in 
the  engraving.  Into  the  first,  E,  the  water  rises 
at  a  given  pressure,  say  one  pound,  and  closes 
the  draught  to  the  fire  by  the  ash-pit  and  draught- 
door  M.  This  exclusion  of  air,  with  the  radia- 
tors in  operation  at  the  same  time,  will  prevent 
the  increase  of  the  pressure.  But  should  the 
radiators  not  be  open  to  use  the  steam,  or  the 
draught-door  be  accidentally  held  open,  the  col- 
umn of  water  will  continue  to  rise,  until  at  the 
pressure  of  H  lb.  it  flows  into  the  second  bowl, 
E,  and  lifts  the  lever  attached  to  the  feed-door 
i,  which  opens  and  causes  the  draught  to  pass 
over  the  fire  instead  of  underneath  and  through 
it.  This  reversal  of  the  draught  has  the  effect 
to  deaden  the  fire  at  once  and  stop  the  genera- 
tion of  steam.  A  slight  additional  pressure  forces 
the  water  of  the  column  into  the  third  bowl,  G, 
and  lifts  the  lever  attached  to  the  escape-valve 
H,  which  allows  all  excess  of  steam  above  that 
pressure  to  pass  freely  off  through  the  waste- 
pipe  I.  C  C  are  wrought-iron  steam-pipes  for  conducting  the  steam  from  the  boiler  to  the  radiators. 
The  radiators  are  made  of  two  plates  of  bloom-iron.  The  front  plate  is  stamped  with  conical  de- 
pressions about  three-eighths  of  an  inch  in  depth,  2^  inches  in  width,  and  3^  inches  from  centre 
to  centre.  The  back  plate  is  plain,  and  the  two  are  riveted  closely  together,  with  copper  rivets  at 
each  point  of  indentation,  and  the  edges  of  each  plate  are  twice  doubled,  or  double-seamed  over  a 
leaded  packing  cord,  and  hammered  down  to  a  smooth  bead  about  one-fourth  of  an  inch  in  width. 

This  concave  surface  gives  strength  to  the  radiators,  and  adds  much  to  their  radiating  power.  The 
entire  thickness  of  the  radiator  is  about  half  an  inch.  On  one  of  the  lower  corners  of  the  radiators 
is  a  valve  to  open  when  steam  is  to  be  admitted,  and  closed  when  steam  is  to  be  excluded.  An  air- 
key  is  placed  on  the  opposite  upper  corner,  to  regulate  the  amount  of  steam  to  be  admitted.  No 
steam  will  enter  any  part  of  the  radiator  until  that  part  is  emptied  of  air.  By  closing  this  air-key 
when  any  desired  portion  of  the  radiator  is  heated,  the  other  portion  will  remain  inoperative  and  cold. 
In  Fig.  2322  is  a  radiator  of  this  type,  shown  attached  to  the  boiler. 



Instead  of  placing  radiators  directly  in  the  rooms  in  large  buildings,  such  as  hotels,  they  are  some- 
times inclosed  in  cases  in  the  walls,  usually  under  the  windows.  Each  case  has  a  register  which 
opens  into  the  apartment.  Steam  is  kept  on  constantly,  and  instead  of  graduating  the  heat  by 
operating  valves  connected  with  the  radiator,  the  occupant  of  the  room  does  so  by  opening  the  register 
more  or  less. 

Steam-Heating  by  Indirect  Radiation. — In  Fig.  2323  is  represented  Messrs.  Baker,  Smith  &  Co.'s 
arrangement  for  warming  and  ventilating  by  indirect  radiation ;  that  is,  by  having  the  heating  stacks 
or  radiators  placed  below  (in  the  cellar  or  some  lower  room)  instead  of  within  the  rooms  to  be 
warmed.  At  the  left  is  shown  the  boiler,  with  its  fire-regulating  attachments,  water-feeder,  safety- 
vent,  etc.  At  the  right  of  the  boiler  are  heating-stacks  within  chambers.  To  these  chambers  is 
connected  an  air-duct,  through  which  fresh  outdoor  air  passes  to  be  heated.  The  heating-stacks,  as 
shown,  are  connected  with  the  boiler  by  two  pipes ;  the  upper  one  supplies  the  steam,  and  the  lower 
one  returns  the  water  of  condensation  to  the  boiler.  Two  rooms  on  the  first  floor  above  the  appara- 
tus are  represented  as  being  warmed  and  ventilated.  Any  number  of  rooms  directly  over,  on  other 
floors,  can  be  warmed  and  ventilated  from  the  same  heating-chamber ;  and  any  number  of  heating- 
chambers  can  be  supplied,  to  suit  the  size  of  the  building. 
Heating  by  Hot  Water. 

Hot-water  apparatus  may  be  resolved  into  two  distinct  forms  or  modifications,  dependent  on  the 
temperature  of  the  water.  In  the  first  form  the  water  is  at  or  below  the  ordinary  temperature  of 
boiling.  In  this  arrangement  the  pipes  do  not  rise  to  any  considerable  height  above  the  level  of  the 
boiler,  so  that  the  apparatus  need  not  be  of  extraordinary  strength.  One  pipe  rises  from  the  top  of 
the  boiler,  and  traverses  the  places  to  be  warmed,  and  returns  to  terminate  near  the  bottom  of  the 
boiler.  Along  this  tube  the  heated  water  circulates,  giving  out  its  heat  as  it  proceeds.  The  boiler 
may  be  open  or  closed.  If  open,  the  tube  when  once  filled  with  water  acts  as  a  siphon,  having  an 
ascending  current  of  hot  water  in  the  shorter  leg,  and  a  descending  current  of  cooled  water  in  the 
longer  leg.  If  the  boiler  be  closed,  the  siphon  action  disappears,  and  the  boiler  with  its  tubes  be- 
comes as  one  vessel.  In  the  second  form  of  apparatus,  the  water  is  heated  to  350°  and  upward,  and 
is  therefore  constantly  seeking  to  burst  out  as  steam,  with  a  force  of  70  lbs.  and  upward  on  the 
square  inch,  and  can  only  be  confined  by  very  Btrong  or  high-pressure  apparatus.  The  pipe  is  of 
iron,  about  an  inch  in  diameter,  made  very  thick.  The  length  extends  to  1,000  feel  and  upward ; 
and  where  much  surface  is  required  for  giving  out  heat,  the  pipe  is  coiled  up  like  a  screw.  A  simi- 
lar coil  is  also  surrounded  by  the  burning  fuel,  and  serves  the  place  of  a  boiler. 

The  Baker,  Smith  &  Co.  Hot-  Winter  System. — In  this  system  the  entire  apparatus,  except  a  space 
provided  for  air,  is  filled  with  water,  the  joints  being  made  absolutely  tight.  When  the  appara- 
tus is  firmly  screwed  together  on  the  premises  where  it  is  to  be  employed,  the  air  from  the  interior 
is  expelled  by  means  of  a  pump.  By  the  same  pump  the  whole  is  then  subjected  to  a  hydrostatic 
test  of  at  least  400  lbs.  pressure  to  every  square  inch,  with  a  view  to  permanency.     Then  water, 

which  is  saturated,  or  nearly  so, 
.  with  salt  to  prevent  freezing,  is 
pumped  in,  till  the  entire  internal 
space,  with  tin'  exception  of  an  air- 
chamber,  is  full  of  water.  When 
the  whole  apparatus  has  been 
proven  to  be  perfectly  water-  and 
air-tight,  it  is  sealed  by  the  safety- 
valve,  and,  as  no  evaporation  is 
allowed,  theoretically  no  more  wa- 
ter need  ever  be  added,  but  prac- 
tically an  occasional  addition  of  a 
small  quantity  is  required.  Im- 
mediately on  the  application  of 
fire  in  the  boiler,  the  adjacent  wa- 
ter feels  its  influence,  and  begins 
to  circulate  and  impart  a  gentle 
warmth  to  the  radiating  pipes.  As 
the  fire  increases,  so  does  the  tem- 
perature of  the  water  and  the 
pipes,  rising  through  all  the  grades 
of  temperature  from  lukewarm  to 
that  of  steam,  till  the  desired  de- 
grees of  heat  are  reached.  Be- 
sides the  regulation  at  the  boiler, 
the  heat  of  the  water  radiator, 
when  placed  within  a  room,  is 
nicely  graduated  by  a  single  valve. 
By  turning  this  valve  the  aperture 
for  the  flow  of  the  water  is  re- 
duced, and  it  circulates  proportion- 
ately cooler.  In  this  manner  one  room  may  be  warmed  by  tepid  water,  while  other  rooms  have  the 
full  heat  of  the  water. 

A  portable  apparatus  of  this  kind  for  heating  railway  cars  is  represented  in  Fig.  2324.  It  consists 
of  a  simple  fire-proof  stove,  occupying  only  two  feet  circle  of  floor  space  in  one  corner  of  the  ear ;  a 
dull  fire,  that  consumes  but  about  a  peck  of  coal  in  12  hours,  warms  the  water,  which  circulates 



I . 








through  pipes  run  under  each  seat  entirely  around  the  car,  giving  each  passenger  the  most  agreeable 
foot-warmer  of  hot  water,  the  heat  of  which  is  evenly  maintained  against  all  currents  of  air,  and  is 
unaffected  by  the  motion  of  the  car.     By  this  plan,  nearly  the  entire  heat  of  the  fire,  instead  of  con- 
centrating at  the  stove,  is  taken  up  and 
distributed  at  the  very  point  where  heat  is 

Cowan's  System  of  Hot-  Water  Heating, 
illustrated  in  Fig.  2325,  is  largely  used  in 
Europe  for  heating  greenhouses.  It  em- 
bodies a  means  of  utilizing  the  waste  heat 
of  a  lime-kiln.  L  is  an  egg-shaped  kiln- 
chamber  about  8  feet  in  depth.  C  is  the 
main  boiler,  serving  as  a  cover  to  the  kiln. 
D  is  an  annular  boiler,  communicating  with 
the  boiler  C  through  the  pipes  F.  G  G 
are  the  return-mains,  completing  the  cir- 
culation for  the  return  of  cooled  water  to 
the  boilers,  and  also  for  keeping  open  com- 
munication with  the  expansion-cistern  H. 
This  cistern  H  acts  as  a  safety-valve  for 
the  whole  apparatus.  The  condensed  wa- 
ter from  it  is  returned  to  the  annular  boil- 
er D  through  the  perpendicular  pipe  1. 
M  is  a  valve  in  the  flow-pipe  to  the  ex- 
pansion-cistern H.  The  pipes  E  commu- 
nicate with  all  the  premises  to  be  warmed, 
and  through  the  valve  M  with  the  com- 
pensating cistern  H.  A  blow-off  cock  for 
the  annular  boiler  is  necessary.  A  com- 
plete circulation  of  any  length  is  claimed 
for  this  apparatus,  which  can  be  erected 
anywhere  outside  the  buildings  to  be  heat- 
ed. In  the  extensive  hothouses  of  Hat- 
field Park,  England,  7,000  feet  of  4-inch 

pipe  are  heated  in  this  way,  and  one  consumer  uses  the  furnace  or  kiln  for  the  manufacture  of  coal* 
gas,  obtaining  this  commodity  at  a  very  moderate  expense.     The  kiln  is  also  used  for  lime-burning, 
the  product  being  sold,  and  the  expense  of  heating  is  thus  reduced. 
HEDDLE.     See  Looms. 

HEEL-FORMING  MACHINE.     See  Shoe  Machinery. 
HEEL-POLISHING  MACHINE.     See  Shoe  Machinery. 

HOISTING  ENGINES.     See  Elevators,  Engines  (Steam  Hoisting),  and  Mine  Appliances. 
HOISTS.     See  Elevators. 
HOLLANDER.     See  Paper-making  Machinery. 

HORSE-POWER.     For  discussion  of  this  term  as  the  measure  of  the  capacity  of  a  motor,  see  En- 
gines, Designing  of,  and  Dynamics.     The  name  is  also  applied  to  mechanism  by  which  the  strength 

of  a  horse  is  advantageous- 
ly utilized  for  driving  ma- 
chines of  various  kinds. 

Figs.  2326  and  2327  repre- 
sent Bogardus's  horse-power 
arranged  for  different  pur- 
poses. The  base-frame  is 
cast  into  one  piece,  consist- 
ing of  the  central  hub  and 
the  outer  ring,  connected  by 
radial  arms  and  standing  on 
legs.  The  central  hub  is  cast 
with  a  hollow  standard  prop- 
erly turned  with  a  slight  ta- 
per, to  which  is  fitted  a  sleeve 
that  turns  thereon  freely  but 
accurately,  and  resting  on 
the  upper  surface  of  the  hub , 
and  likewise  with  this  sleeve, 
and  making  part  thereof,  is 
cast  a  wing,  to  which  is  se- 
cured by  bolts  the  horse-beam 
or  lever  by  which  the  whole 
is  operated.  The  other  end 
of  the  wing  is  provided  with 
another  sleeve  cast  there- 
with, and  parallel  to  the  first,  to  which  is  fitted  accurately  (but  so  as  to  admit  of  turning  freely)  the 
arbor  of  the  planet-wheel  and  planet-wheel  pinion,  the  former  being  at  the  top  and  the  latter  at  the 



bottom.  One  of  these,  either  the  wheel  or  the  pinion,  can  be  permanently  attached  to  the  arbor,  and 
the  other  keyed  on  after  it  has  been  inserted  in  the  sleeve.  The  cogs  of  the  pinion  of  the  planet- 
wheel  take  into  the  cogs  formed  in  the  inner  periphery  of  the  rim  of  the  base-frame,  and  this  may 
be  called  the  master-wheel ;  and  the  cogs  of  the  planet-wheel  take  into  the  cogs  of  and  drive  the 

central  pinion  on  the  upper 
2327-  end  of  a  vertical  shaft  that 

passes  through  and  turns  free- 
ly but  accurately  in  the  cen- 
tral hollow  standard,  which  is 
adapted  to  it,  the  driving-pul- 
ley being  keyed  on  the  lower 
end  and  below  the  hub.  A 
band  from  the  driving-pulley 
can  be  carried  under  the  frame 
and  between  the  legs  to  any 
P  place  required,  in  the  usual 
manner,  to  drive  any  piece  of 
machinery ;  but  if  desired,  the 
driving-pulley  can  be  attached 
to  the  central  shaft  above  the 
central  pinion. 

Fig.  2327  shows  the  appa- 
ratus as  arranged  to  carry 
the  belt  from  the  horizontal 
pulley  under  the  foot-path  on 
which  the  horse  walks.  As 
represented  in  Fig.  2326,  the 
shaft  may  be  carried  under  the  foot-path  or  to  a  floor  above.  The  diameter  of  the  path  should  be 
from  25  to  30  feet,  and  the  Bpeed  of  the  horse  should  be  at  the  rate  of  about  2i  miles  per  hour. 

Fig.  2328  represents  a  form  of  horse-power  arranged  on  a  different  principle  from  the  foregoing. 
In  this  the  weight  of  the  horse  as  well  as  the  animal's  muscular  power  is  utilized.  The  wooden  step- 
boards  D  are  arranged  in  an  endless  belt,  and  are  supported  by  a  series  of  small  rollers  which  rest 


on  inclined  tracks  or  ways.  The  apron  passes  over  and  rotates  the  drum  A,  which  by  a  pinion  turns 
a  sear,  on  the  opposite  end  of  the  axle  of  which  is  a  wheel,  which  is  governed  or  held  by  a  brake- 
lever.  The  horse  walks  upon  the  step-boards,  and  so  causes  the  apron  to  rotate.  Power  is  taken 
off  by  suitable  belting. 

A  similar  arrangement  for  utilizing  horse-power  in  driving  a  railway  car  is  represented  in  Fig. 

2329,  the  device  being  termed  an  "  impulsoria."  Motion  is  imparted  from  the  moving  platform  to 
the  axles  by  means  of  gearing.  It  is  hardly  necessary  to  point  out  that  this  is  simply  an  ingenious 
way  of  wasting  power,  and  that  the  force  of  the  animal  would  be  much  more  economically  exerted 
by  direct  traction  of  the  vehicles. 



HORSE-POWER  (H.  P.).    See  Engines,  Heat. 

HORSE-SHOE  MACHINERY.     See  Forging. 

HOUSING.     See  Carpentry. 

HULLERS,  COFFEE  AND  RICE.  Coffee  Hullers  are  machines  for  removing  the  husk  or  hull 
from  coffee  grains. 

Brown's  Huller. — In  the  apparatus  constructed  by  Messrs.  W.  A.  Brown  &  Co.,  of  Lynn,  Mass., 
represented  in  Fig.  2329  a,  the  hulling  is  accomplished  by  drawing  the  grains  on  an  endless  chain  or 
apron  consisting  of  a  series  of  corrugated  iron  pads,  which  are  made  to  pass  underneath  a  series  of 
steel  keys  or  fingers  held  in  place  by  coiled  steel  springs,  causing  them  to  adjust  themselves  to  the 
size  of  the  beans  which  pass  under  them,  so  that  a  small  bean  cannot  pass  through  unhulled  and  a 
large  bean  passes  through  unbroken ;  thus  hulling  both  small  and  large  beans.  The  coffee  and  the 
hulls  fall  from  the  hulling  plates,  or  pads,  on  to  a  set  of  sieves,  which  are  so  arranged  that  they  are 
continually  in  motion  and  keep  the  hulls  and  coffee  in  line  of  the  current  of  air  produced  by  the  fan 
which  is  located  in  the  front  part  of  the  machine,  and  is  arranged  so  as  to  blow  out  the  hulls  and 

allow  the  coffee  to  fall  through  the  sieves  on  the  chute,  which  conducts  it  into  the  receptacle  placed 
to  receive  it. 

The  coffee  being  free  from  hulls,  it  is  necessary  to  give  it  a  thorough  cleaning  and  polishing, 
thereby  removing  the  fine  silver  skin  which  closely  adheres  to  the  beans.  An  improved  device  for 
this  purpose  by  the  above-named  makers  consists  of  a  heavy  perforated  brass  cylinder  arranged 
horizontally  in  a  heavy  wooden  frame.  Through  the  cylinder  passes  a  shaft  on  which  are  a  number 
of  hard-wood  floats.  The  shaft  rotates  at  the  rate  of  about  100  revolutions  per  minute.  By  means 
of  the  floats  the  coffee  is  thoroughly  agitated,  and  thus  cleaned  and  polished. 

Guardiola's  Huller. — The  coffee-hulling  and  polishing  machine  devised  by  Sr.  Jose  Guardiola,  of 
Guatemala,  consists  essentially  of  a  mortar  and  pestle,  the  construction  being  such  that  the  coffee  is 
cleaned  and  polished  by  the  friction  of  one  grain  against  the  other  moving  in  the  broken  chaff.  The 
pestle  is  a  sieve  having  on  its  surface  oblique  projecting  ribs,  set  at  proper  distances  from  one 
another  so  as  to  form  channels.  The  interior  of  the  mortar  is  also  provided  with  ribs  and  channels. 
The  pestles  drop  simultaneously  into  the  mortars,  and  the  coffee  is  forced  to  move  up  and  down  the 
channels.  The  husk  is  broken,  and  finally  pulverized.  Each  mortar,  it  is  claimed,  will  clean  from 
150  to  200  lbs.  of  coffee  per  hour. 

Squier's  Coffee  Hulk};  it  is  claimed,  makes  the  coffee  in  a  large  degree  hull  itself,  by  forcing  the 
grains  to  rub  against  each  other  under  pressure,  thus  preventing  all  breakage  of  the  grains  and 
polishing  them  during  the  process  of  hulling.     An  iron  cylinder  is  provided  through  which  runs  a 


screw  with  peculiar  broken  threads.  At  one  end  of  the  cylinder  is  a  hopper  into  which  the  coffee  is 
fed,  and  a  peculiar  propeller  forces  the  coffee  into  the  cylinder,  where  the  screw  keeps  the  grains  in 
constant  agitation,  grinding  against  each  other  until  the  husk  is  broken  and  the  silver  skin  worn  off, 
and  the  coffee  comes  out  hulled  and  polished.  It  has  then  only  to  go  to  the  separator  to  have  the 
chaff  blown  off  and  the  grains  sorted  according  to  size,  when  it  is  ready  for  market. 

Rice  Huller. — The  essential  requirement  of  this  machine  is  to  hull  the  rice  without  breakage.  An 
ingenious  machine  for  this  purpose,  made  by  Messrs.  George  L.  Squier  &  I3ro.  of  Buffalo,  N.  Y., 
consists  of  two  disks  running  one  on  the  other  like  millstones.  The  upper  disk  is  stationary,  and 
the  lower  one,  instead  of  having  a  rotary  motion  like  a  millstone,  has  a  reciprocating  motion.  The 
unhulled  rice  passes  from  the  hopper  through  an  eye  in  the  centre  of  the  upper  disk,  and,  the  disks 
being  grooved  in  a  peculiar  manner,  the  rice  spreads  over  the  face  of  the  lower  disk,  and  is  rolled 
and  rubbed  between  the  two  disks  until  the  hulls  are  removed,  when  it  passes  out  over  the  edge  of 
the  lower  disk  and  falls  into  a  receptacle.  Increased  capacity  is  attained  by  multiplying  the  disks, 
all  being  put  into  one  frame  and  actuated  by  a  single  pitman.  In  all  rice  there  is  a  certain  amount 
of  small,  green,  shriveled,  or  imperfect  grains,  that  will  pass  through  any  huller  unhulled ;  and  one 
difficulty  of  rice-bulling  has  been  to  dispose  of  these.  It  is  too  expensive  to  pick  them  out  by  hand, 
and  therefore  it  has  been  the  custom  in  rice-mills  to  dump  all  the  rice  as  it  comes  from  the  hulling 
stones  into  mortars,  and  pound  it  until  the  hulls  ore  worn  off  from  these  few  unhulled  grains.  A 
separator  has  been  devised  by  the  above  manufacturers  which  is  claimed  to  Beparate  the  unhulled 
from  the  hulled  grains,  and  to  clean  rice  and  save  every  grain  with  little  or  no  breakage. 

HYDRAULIC  ENGINE.    See  Engines,  Water-Pressure. 

HYDRAULIC  FORGING.     See  Forging. 

1 1 V I  (RAULIO  MAIN.     See  Gas  Apparatus. 

HYDRAULIC  PRESS.     See  Preps,  1 1  vim  a  cue. 

HYDRODYNAMICS  treats  of  the  laws  of  liquids  in  motion.  One  of  its  most  important  prin- 
ciples is  that  which  determines  the  velocity  of  jets  which  issue  from  orifices  at  various  depths  in  the 
sides  of  vessels  containing  liquids,  and  depends  upon  the  laws  of  hydrostatic  pressure.  11'  an  orifice 
is  made  in  the  side  of  a  vessel  containing  a  liquid,  the  liquid  will  issue  from  it  with  a  velocity  equal 
to  that  which  a  heavy  body  would  acquire  in  falling  through  the  vertical  distance  between  the  sur- 
face of  the  liquid  and  the  orifice.  If  the  jet  is  directed  upward,  it  will  ascend,  theoretically,  to  a 
level  with  the  surface  of  the  liquid  ;  but  practically  it  will  fall  short  of  this  in  consequence  of  fric- 
tion at  the  orifice,  and  of  the  resistance  offered  by  the  air.  At  first  sight  it  would  appear  that  the 
velocity  of  efflux  would  be  proportional  to  the  pressure ;  but  an  analysis  of  the  case,  apart  from  the 
test  of  experiment,  will  show  that  this  cannot  be,  for  in  no  case  can  the  jet  be  projected  higher 
than  the  surface  of  the  liquid.  If,  in  general  terms,  the  velocity  of  a  jet  were  in  proportion  to  the 
pressure  at  the  point  of  issue,  a  column  of  mercury  would  throw  a  jet  with  13|  times  the  velocity 
that  an  equal  column  of  water  would ;  but  it  must  be  perceived  that  a  column  of  mercury  can  only 
propel  a  jet  as  high  (theoretically)  as  the  surface,  and  therefore  to  the  same  height  as  an  equal  col- 
umn of  water  can.  Now,  there  can  be  no  doubt  that  the  pressure  of  mercury  at  the  same  depth  is 
13-J  time-  that  of  water;  but  mercury,  being  also  \'.\\  times  as  heavy  as  water,  has  13.}  times  as 
much  inertia,  and  therefore  requires  so  many  times  as  much  force  to  give  it  the  same  initial  velocity. 
The  velocity  with  which  a  liquid  escapes  from  an  orifice  varies  as  the  square  root  of  the  depth  below 
the  surface ;  so  that  when  the  points  of  escape  are  1,  4,  9,  and  16  feet  in  depth,  the  initial  velocities 
will  be  as  1,  2,  3,  and  4.  This  is  the  celebrated  theorem  of  Torricelli,  which  he  deduced  from  the 
laws  of  falling  bodies.  As  the  velocity  of  a  falling  body  is  in  proportion  to  the  time  of  its  fall,  it 
will  be  in  proportion  to  the  square  root  of  the  height  fallen  through,  and  is  represented  by  the 
formula  U=  Vigh,  in  which  g  is  the  accelerating  force  of  gravity  (=  32.2),  and  h  the  height.  (See 
Dynamics.)  A  jet  issuing  from  the  side  of  a  vessel  describes,  theoretically,  a  parabola,  precisely 
as  in  the  case  of  a  solid  projectile  ;  for  the  impelling  force  and  the  force  of  gravity  act  upon  the  jet 
in  the  same  manner,  and  the  resultant  force  gives  it  the  same  direction.  The  range,  or  distance  to 
which  the  jet  is  projected,  is  greatest  when  the  angle  of  elevation  is  45°,  and  is  the  same  for  eleva- 
tions which  are  equally  above  or  below  45°,  as  60°  and  30".  The  resistance  of  the  air  however  alters 
the  results,  and  the  statement  is  only  true  when  the  jet  is  projected  into  a  vacuum. 

If  a  vessel  filled  with  water  have  orifices  made  in  its  side  at  equal  distances  in  a  vertical  line  from 
the  top  to  the  bottom,  a  stream  issuing  from  an  orifice  midway  between  the  surface  and  the  bottom 
will  be  projected  farther  than  any  of  the  streams  issuing  from  the  orifices  above  or  below.  This 
may  be  demonstrated  by  the  adjoining  diagram,  Fig.  2330.  Let  a  semicircle  A  F  E  be  described  on 
the  side  of  a  vessel  of  water,  its  diameter  being  equal  to  the  height  of  a  liquid.  The  range  of  a  jet 
issuing  from  either  of  the  orifices  B,  C,  or  D  will  be  equal  to  twice  the  length  of  the  ordinates  BF, 
CI,  or  B  K  respectively ;  and  therefore  jets  issuing  from  B  and  D  will  meet  at  a  point  /Zona  level 
with  the  bottom,  and  twice  the  length  of  the  ordinates  B  F  axxA  D  K.  Now,  as  the  ordinate  CI  is 
the  greatest,  the  range  of  the  jet  issuing  from  C  will  be  greater  than  that  of  any  other  jet.  The 
amount  of  water  escaping  in  one  second  from  an  orifice  would,  theoretically,  be  equal  to  a  cylinder 
having  a  diameter  equal  to  that  of  the  orifice,  and  a  length  equal  to  the  distance  through  which  a 
body  will  move  with  a  uniform  velocity  after  it  has  fallen  through  a  height  equal  to  the  vertical  dis- 
tance between  the  surface  of  the  liquid  and  the  orifice.  If  this  distance  is  16.1  ft.,  the  velocity 
acquired  will  be  32.2  ft.  per  second,  and  therefore  the  theoretical  quantity  discharged  from  an  ori- 
fice 4  in.  in  diameter,  whose  centre  is  16.1  ft.  below  the  surface,  would  be  equal  to  a  cylinder  4  in. 
in  diameter  and  32.2  ft.  long,  and  containing  4,828.5  cubic  inches,  or  about  21.83  gallons. 

The  actual  discharge  from  a  thin  orifice  not  furnished  with  an  ajutage  is  however  much  less,  being 
only  about  two-thirds  of  the  theoretical  amount.  The  loss  is  owing  partly  to  friction,  but  mainly  to 
the  interference  of  converging  currents  moving  within  the  vessel  toward  the  orifice.  This  interfer- 
ence may  be  shown  by  employing  a  glass  vessel. having  a  perforation  in  its  bottom,  as  represented  in 



Fig.  2331.  If  particles  of  some  opaque  substance  having  nearly  the  same  specific  gravity  as  water, 
so°that  they  will  remain  suspended  in  it  for  a  space  of  time,  be  mingled  with  the  water,  they  will  be 
seen  to  move  in  the  direction  indicated  by  the  lines  in  the  figure,  which  are  nearly  direct.  If  the  jet 
is  carefully  observed,  it  will  be  seen  that  it  is  not  cylindrical,  and  that  for  a  distance  from  the  orifice 



/?  iv._->i 





of  about  half  its  diameter  it  resembles  a  truncated  cone  with  the  base  at  the  orifice.  This  contrac- 
tion of  the  stream  is  called  the  vena  contractu,  and  its  smallest  diameter  is  stated  to  be  from  0.6  to 
0.8  of  that  of  the  orifice.  When  the  stream  has  a  direction  downward  nearly  vertical,  it  continues 
to  diminish  beyond  the  vena  contracta,  in  consequence  of  the  increased  velocity  caused  by  the  force 
of  gravity,  the  size  being  in  the  inverse  proportion  to  the  velocity.  The  increased  velocity  at  the 
vena  contracta  is  due  to  the  pressure  which  forces  the  particles  of  water  into  a  narrower  channel. 
As  the  jet  continues  to  fall,  it  forms  a  series  of  ventral  and  nodal  segments,  as  shown  in  Fig.  2332. 
The  ventral  segments  are  composed  of  drops  elongated  horizontally,  as  seen  at  a  a  «,  while  the  nodal 
segments  are  elongated  vertically,  as  seen  at  b  b  b  ;  and  as  the  segments  have  fixed  positions,  it  follows 
that  the  drops  in  falling  are  alternately  elongated  vertically  and  horizontally.  If  the  orifice  is  in  the 
side  of  the  vessel  and  discharges  horizontally,  the  size  of  the  stream  does  not  diminish  in  the  same 
manner  as  when  falling  vertically,  and  it  is  sooner  broken.  If  a  cylindrical  tube  or  ajutage  whose 
length  is  from  two  to  three  times  its  diameter  is  fitted  to  the  orifice,  the  rate  of  efflux  may  be  in- 
creased to  80  per  cent,  of  the  theoretical  amount.  The  velocity  will  be  somewhat  diminished,  but 
the  vena  contracta  will  be  larger  in  proportion.  If  the  inner  end  of  the  ajutage  has  a  conical  shape 
with  the  base  toward  the  interior,  the  efflux  may  be  further  increased  to  95  per  cent. ;  and  it  has 
been  found  that  if  the  outer  end  of  the  tube  is  also  enlarged,  the  efflux 
may  be  still  further  increased  to  very  nearly  the  theoretical  amount,  say 
98  per  cent.  When  a  cylindrical  ajutage  is  used,  there  will  be  a  partial 
vacuum  formed  between  the  sides  of  the  tube  and  the  contracted  vein,  as 
shown  in  Fig.  2333.  If  a  pipe  ascending  from  a  reservoir  of  water  is  let 
into  this  part  of  the  ajutage,  the  water  will  rise  in  the  pipe ;  and  if  the 
height  is  not  too  great,  the  vessel  may  be  emptied. 

The  resistance  offered  by  conduits  is  a  subject  of  great  importance  in 
practical  hydrodynamics,  upon  which  extended  experiments  have  been 
made.  When  the  length  of  the  ajutage  bears  more  than  a  certain  pro- 
portion to  its  diameter,  the  efflux  is  reduced  to  about  the  same  amount  as 
when  the  stream  issues  through  a  thin  orifice,  that  is,  about  62  per  cent, 
of  the  theoretical  amount.  With  a  pipe  l^  in.  in  diameter  and  30  ft. 
long,  the  efflux  will  be  only  about  half  that  from  a  thin  orifice,  or  31  per 
cent,  of  the  theoretical  amount.  This  reduction  is  caused  by  friction 
between  the  liquid  and  the  tube,  as  well  as  between  its  particles,  and  is  greater  with  cold  than  with 
warm  liquids.  This  resistance  to  motion,  or  approach  to  rigidity,  which  is  conferred  by  cold,  is  called 
viscosity,  and  is  a  principle  which  has  to  oe  taken  into  account  in  nearly  all  very  careful  hydraulic 

Resistance  of  Liquids  to  the  Motion  of  Solid  Bodies. — This  will  depend  upon  the  form  and  size  of 
the  body.  The  following  are  two  important  laws:  1.  With  the  same  velocity,  the  resistance  is  pro- 
portional to  the  extent  of  surface  applied  by  the  solid  to  the  liquid  in  the  direction  of  motion.  2. 
With  the  same  extent  of  surface,  the  resistance  is  proportional  to  the  square  of  the  velocity.  These 
laws  may  be  demonstrated  experimentally,  but  their  truth  will  also  be  apparent  from  the  following 
considerations.  In  regard  to  the  first  law,  it  will  be  easily  understood  that  with  the  same  velocity 
the  amount  of  water  displaced  will  be  the  measure  of  resistance,  and  that  a  surface  of  two  square 
feet  will  displace  twice  as  much  as  one  of  one  square  foot.  The  second  law  is  not  so  evident,  but 
will  be  made  clear  by  considering  that  with  a  given  surface,  when  the  velocity  is  doubled,  twice  the 
quantity  of  liquid  will  move  through  twice  the  space  in  the  same  time,  and  will  therefore,  according 
to  the  principles  of  mechanics,  have  a  fourfold  momentum.  The  resistance,  therefore,  offered  to  a 
plane  surface  moving  at  right  angles  against  a  liquid,  is  measured  by  the  area  of  the  surface  multi- 
plied into  the  square  of  the  velocity.     It  has  been  found  that  a  square  foot  surface,  moved  through 



water  with  a  velocity  of  32  ft.  per  second,  meets  with  a  resistance  equal  to  a  weight  of  1,000  lbs. 
When  the  motion  of  a  body  in  a  liquid  is  very  slow,  say  less  than  1  in.  per  Becond,  depending  on  the 
size  of  the  body,  the  larger  body  requiring  to  move  more  slowly,  the  above  laws  are  not  rigidly  fol- 
lowed, but  the  resistance  is  divided  into  two  components,  one  of  which  is  proportional  to  the  simple 
velocity,  and  the  other  to  the  square  of  the  velocity.  The  most  accurate  results  in  experimenting 
with  slow  motions  were  obtained  by  Coulomb,  who  used  his  torsion  balance.  One  of  the  most  inter- 
esting problems  in  mathematics  has  been  to  determine  the  form  of  a  solid  which  will  meet  with  the 
least  resistance  in  moving  through  water.  This  form  is  called  the  "  solid  of  least  resistance,"  and  is 
approached  as  near  as  practicable  in  the  construction  of  ships. 

The  complete  demonstration  of  the  principles  of  hydrodynamics  involves  the  higher  mathematics, 
and  their  elucidation  in  full  would  require  greater  space  than  can  here  be  afforded.  For  this  the 
reader  is  referred  to  the  special  treatises  on  the  subject. 

For  a  full  discussion  of  Ilerr  Kutter's  new  formula  for  mean  velocity  of  discharge  of  rivers  and 
canals,  see  a  work  bearing  that  title,  translated  by  Louis  D'A.  Jackson,  A.  I.  ('.  E.  (London  and 
N.  iw  York,  1876);  also,  for  a  complete  exposition  of  the  science,  "  Hydraulic  Manual  and  Statistics," 
by  the  same  author.  The  following  works  may  also  be  consulted:  "Practical  Bydraulics,"  by 
Thomas  Box  (4th  edition);  "Manual  of  Hydrology,  containing  Hydraulic  and  other  Tables,"  etc.,  by 
Nathaniel Beardmore,  C.  E.;  Tredgold's  " Tracts  on  Hydraulics";  "Hydraulic  Engineering,  a  Prize 
Essay  on  the  Encroachment  of  the  Sea  between  the  River  Mersey  and  the  Bristol  Channel,"  by  J.  E. 
Thomas  (1866);  "Hydraulics  of  Great  Rivers,  being  Observations  and  Surveys  on  the  largest  Rivers 
of  the  World,"  by  J."  J.  Levy,  with  plates  and  charts;  "  Mechanics  of  Fluids,"  by  Alexander  Jamie- 
son,  LL.D.  ;  "Engineers'  Pocket-Books"  of  Haswell,  Molesworth,  and  Trautwine;  "A  Descriptive 
and  Historical  Account  of  Hydraulic  and  other  Machines  for  raising  Water,"  by  Thou, as  Ewbank 
(15th  edition).  See  also  Aqueduct,  Barrage,  Canals,  Drainage,  Pumps,  Water-Wheels,  and 

HYDROMETER,  or  AREOMETER.*  An  instrument  for  determining  the  specific  gravity  of  li- 
quids. It  generally  consists  of  some  buoyant  body,  as  hollow  glass  or  copper,  weighted  at  the  bottom 
and  supporting  a  graduated  stem,  or  one  having  a  definite  mark.  There  are  two  kinds,  those  of  con- 
stant and  those  of  variable  immersh  n.  Those  of  constant  immersion  are  made  to  sink  in  the  tested 
liquid,  whether  dense  or  light,  to  the  same  depth,  by  balancing  with  weights.  Those  of  variable  im- 
mersion have  no  movable  weights,  but  rise  or  fall  according  to  the  density  of  the  liquid. 

Nicholson's  hydrometer.  Fig.  2384,  is  of  the  first  kind.  As  usually  constructed,  when  this  instru- 
ment is  immersed  in  water  it  requires  a  weight  of  1,000  grains  to  make  it  sink  to  a  certain  mark  on 
the  stem.  According  to  the  principle  of  Archimedes,  the  weight  of  the  instrument,  together  with 
the  1,000  grains  which  it  sustains,  is  equal  to  the  weight  of  the  volume  of  water  displaced.  If  the 
instrument  is  placed  in  a  liquid  lighter  or  heavier  than  water,  and  the  weight  changed  until  it  sinks 

W  +  w 
to  the  same  depth,  the  specific  gravity  of  the  liquid  will  be  indicated  by  the  formula  g  =  __ — _ _ . 

M    +  1,000 

where  W  is  the  weight  of  the  instrument,  and  w  that  of  the  weights  placed  upon  the  pan.  If  w  is 
Less  than  1,000  grains,  it  will  show  that  the  liquid  is  lighter  than  water;  and  if  it  is  more  than  1,000 
grains,  it  will  show  that  it  is  heavier.  This  instrument  may  also  be 
used  to  find  the  specific  gravity  of  solids,  or  as  a  delicate  balance. 
For  these  purposes  it  has  a  small  cup  or  wire  cage  suspended  at  the 
bottom  to  hold  the  body,  which  may  be  either  heavier  or  lighter  than 
water.     To  find  the  specific  gravity  of  a  solid,  let  it  be  first  weighed  in 

air,  by  placing  upon  the  pan  a 





piece  of  the  substance  which 
weighs  less  than  1,000  grains. 
Suppose  the  substance  to  be 
sulphur,  and  that  440  grains 
are  required  to  be  added  to 
make  the  instrument  sink 
to  the  mark  on  the  stem, 
the  weight  of  the  sulphur  is, 
evidently,  1,000  —  440  =  560 
grains.  Now,  what  it  loses  if 
weighed  in  water  will  be  the 
weight  of  an  equal  bulk  of 
water,  and  this  will  be  found 
by  placing  it  in  the  cup  or 
cage  at  the  bottom,  and  add- 
ing sufficient  weights  to  those 
in  the  pan  at  the  top  to  bring 
the  mark  to  the  level  of  the 
water.  If  it  requires  the  ad- 
dition of  275.2  grains,  that 
amount  will  represent  the 
weight  of  a  volume  of  water  equal  to  the  sulphur;  consequently  the  specific  gravity  of  the  sulphur 
will  be  ffscs  =  2.03.  If  the  body  is  lighter  than  water,  it  will  of  course  require  the  addition  of 
more  than  its  weight  to  the  pan,  and  for  immersion  it  will  require  to  be  placed  in  the  wire  cage. 

*  From  the  "  American  Cyclopaedia." 


Fahrenheit's  hydrometer  differs  from  Nicholson's  in  being  constructed  of  glass,  and  having  a  con- 
stant weight  of  mercury  in  a  bulb  at  the  lower  end.     Its  use  is  therefore  restricted  to  the  weighing 

Of  hydrometers  of  variable  immersion,  Baume's  is  the  one  most  frequently  used,  and  furnishes  a 
good  example  of  the  class.  Two  instruments,  of  different  forms,  are  represented  in  Figs.  2335  and 
2336.  They  are  made  of  glass ;  their  stems  are  hollow  and  lighter  than  the  fluid  in  which  they  are 
immersed.  Fig.  2335  is  called  a  salimeter,  and  is  used  for  estimating  the  proportion  of  a  salt  or 
other  substance  in  solution.  It  is  graduated  in  the  following  manner :  Being  immersed  in  water  at 
a  temperature  of  12°  C,  the  point  to  which  it  sinks  is  marked  0° ;  it  is  then  placed  in  a  solution  con- 
taining 15  parts  of  common  salt  to  85  of  water,  the  density  of  which  is  about  1.116,  and  the  point  to 
which  it  sinks  is  marked  15,  and  the  interval  divided  into  15  equal  parts;  the  graduation  is  then  ex 
tended  downward,  generally  terminating  at  66°,  which  corresponds  to  the  density  of  sulphuric  acid. 
When  the  instrument  is  to  be  used  for  liquids  lighter  than  water,  the  zero  is  not  placed  at  the  point 
to  which  it  sinks  in  pure  water,  but  at  a  point  to  which  it  sinks  in  a  solution  containing  10  parts  of 
common  salt  to  90  of  water.  The  point  to  which  it  sinks  in  pure  water  was  marked  by  Baume  10°, 
and  the  graduation  was  continued  upward  to  the  highest  point  to  which  the  stem  might  be  immersed 
in  the  lightest  liquid.  Fig.  2336  represents  the  instrument  for  liquids  lighter  than  water.  The  grad- 
uation of  these  hydrometers  is  arbitrary,  and  is  an  indication  of  the  strength  of  the  liquid  only  after 

trial.  i  i       j 

Hare's  hydrometer,  a  very  valuable  instrument,  but  one  which  has  not  been  much  employed,  acts 
upon  the  principle  of  the  barometer,  and  yields  directly  results  of  definite  comparison;  it  is  repre- 
sented in  Fig.  2337.  A  ]yshaped  tube  has  its  legs,  of  equal  length,  placed  in  shallow  vessels,  ope 
containing  the  liquid  to  be  tested,  and  the  other  a  liquid  taken  as  a  standard,  as  water.  A  partial 
vacuum  is  then  produced  in  the  tube  by  exhausting  the  air  by  means  of  an  air-pump,  the  mouth,  or 
otherwise,  making  use  of  the  stop-cock  to  facilitate  the  operation.  It  is  evident  that  the  height  of 
the  liquid' column  will  be  in  the  exact  inverse  proportion  to  the  specific  gravity  of  the  liquids. 

Hydrometers  have  various  names,  according  to  the  purpose  for  which  they  are  used :  as  lactome- 
ters, for  estimating  the  amount  of  cream  in  milk,  or  the  quantity  of  sugar  of  milk  in  the  whey ;  vino- 
meters,  for  estimating  the  percentage  of  alcohol  in  wine  or  cider ;  and  there  are  acidometers  and 

HYDROSTATIC?.  The  mechanical  properties  of  liquids  are  determined  on  the  hypothesis  that 
liquids  are  incompressible.  They  are,  however,  more  compressible  than  most  solids.  If  a  cubic  inch 
of  water  be  pressed  with  15  lbs.  on  each  and  every  side,  the  volume  will  be  diminished  -ixtbooi 
hence  1  lb.  pressure  to  the  square  inch  will  diminish  the  volume  aUiiWff-  If  tlie  water  be  confined 
in  a  perfectly  rigid  prismatic  vessel,  the  compression  would  take  place  entirely  in  the  direction  of 
the  length,  and  would  equal  ^omnrd  of  the  length  for  every  pound  per  unit  of  area  of  the  end  pres- 
sure. Water  therefore  is  nearly  100  times  as  compressible  as  steel.  All  other  liquids  are  more  or 
less  compressible ;  yet,  for  most  practical  purposes,  they  may  be  considered  as  non-elastic  without 
involving'  sensible  error.     Liquids  are  sometimes  defined  as  non-elastic  bodies. 

The  upper  surface  of  a  liquid  contained  in  a  vessel  which  receives  no  pressure  is  called  the  free 
surface.  The  upper  surface  of  water  in  the  atmosphere  is  pressed  downward  by  the  air  with  about 
15  lbs.  to  the  square  inch  ;  yet  such  a  surface  is  often  considered  as  a  free  surface.  The  free  sur- 
face of  small  bodies  of  a  perfect  liquid  at  rest  may  be  considered  as  horizontal,  for  it  will  be  perpen- 
dicular to  the  action  of  gravity ;  but  for  large  bodies  of  liquid  it  is  spherical,  partaking  of  the  gen- 
eral form  of  the  surface  of  the  earth.  A  level  surface  is  one  which  cuts  at  right  angles  the  result- 
ant of  the  forces  which  act  upon  its  particles.  Thus,  in  a  vessel  filled  with  a  heavy  liquid  at  rest,  it 
is  horizontal ;  in  the  ocean,  it  may  be  a  surface  at  any  depth  and  nearly  concentric  with  the  free 
surface.  In  a  cylindrical  vessel  containing  a  perfectly  homogeneous  liquid,  if  the  vessel  be  revolved 
uniformly  about  a  vertical  axis,  the  surface  becomes  a  paraboloid  of  revolution.  In  a  vessel  filled 
with  a  perfectly  homogeneous  liquid  and  drawn  horizontally  with  a  uniform  acceleration,  the  free 
surface  becomes  a  plane.  If  a  perfectly  homogeneous  mass  of  liquid  be  acted  upon  by  a  force 
which  varies  directly  as  the  distance  from  the  centre  of  the  mass,  the  free  surface  will  be  of  spheri- 
cal form ;  if  the  mass  rotates  about  an  axis,  the  form  assumed  will  be  that  of  an  oblate  spheroid, 
which  is  the  shape  of  the  earth. 

It  will  be  obvious  from  the  foregoing  that  each  particle  of  a  liquid  must  exert  and  receive  equal 
pressures  in  all  directions.  If  this  were  not  true,  the  particles  of  a  liquid  could  not  come  to  a  state 
of  rest.  From  this  principle  it  follows  that  equal  surfaces  of  the  sides  of  a  vessel  containing  a 
liquid  receive  equal  pressures  at  equal  depths  below  the  surface  ;  and  also  that  if  a  closed  vessel  be 
filled  with  a  liquid  which  we  will  suppose  to  have  no  weight,  and  if  an  aperture  of  the  size  of  1  square 
inch  be  made  in  one  side  of  it  and  fitted  with  a  piston  upon  which  there  is  exerted  a  pressure  of  10 
lbs.,  there  will  also  be  exerted  the  same  pressure  of  10  lbs.  upon  every  square  inch 
of  the  lateral  surface  of  the  vessel.    Consequently,  if  another  aperture  of  100  square  2338. 

inches  area  be  made  in  the  side  of  the  vessel,  and  a  cylinder  of  the  same  size  be 
fitted  to  it,  a  piston  fitted  to  this  will  receive  a  pressure  of  1,000  lbs.  Upon  this 
principle  the  hydraulic  press  is  constructed. 

In  Fig.  2338,  let  .£  represent  the  large  piston  in  the  vessel  A  B  C  D,  and  F  the 
small  one.  Let  P  represent  the  pressure  on  piston  E,  A  the  area  of  the  orifice  in 
which  this  piston  enters,  p  the  pressure  on  piston  F,  and  a  tha  orifice  to  which  this 
piston  is  fitted.  Then,  according  to  the  principle  noted  above,  a  :  A  ::  p  :  P.  But  the  areas  of 
different  circles  are  to  one  another  as  the  squares  of  their  diameters.  Representing  these  areas^  by 
d  and  D,  we  have  d2  :  D2  ::  p:  P,  in  which  these  values  are  substituted  in  the  first-noted  equation. 
From  this  ratio  we  obtain  p  D2  —  Pd'i.  From  this  we  have  the  following  rules,  the  application  of 
which  to  the  designing  of  hydraulic  presses  will  be  obvious : 


To  find  the  intensity  of  the  pressure  on  the  cylinder-piston,  multiply  the  square  of  the  diameter 
of  the  cylinder  by  the  pressure  on  the  piston  of  the  forcing-pump,  and  divide  the  product  by  the 


square  of  its  diameter ;  or  the  formula,  P  =  -  ...    ■ 

Example.— If  the  diameter  of  the  cylinder  is  5  inches  and  that  of  the  forcing-pump  1  inch,  what 
is  the  pressure  on  the  piston  in  the  cylinder,  supposing  the  pressure  applied  on  the  small  piston  to 

5 *  x  750 

be  equivalent  to  750  lbs  ?     P  = n =  18>'750  lbs- 

To  find  the  pressure  on  piston  F,  or  power  required,  we  have  p  =  -jjj- 

The  diameter  of  the  cylinder  is  obtained  by  the  formula  D  =  \ / ;  and  the  diameter  of  the 

forcing-pump  is  given  by  the  formula  d  =  a/  P-—  .     These  are  very  easily  applied,  as  indicated  by 

the  practical  example  already  given. 

In  designing  hydraulic  presses  the  following  data  will  also  be  found  useful : 

To  determine  the  thickness  of  metal  in  die  cylinder  to  withstand  the  required  pressure:  The 
amount  of  force  which  tends  to  rapture  the  cylinder  along  the  curved  side,  that  is,  to  divide  the 
cylinder  in  halves  lengthwise,  is  equal  to  the  pressure  per  square  inch  on  each  lineal  unit  of  the 
diameter  multiplied  by  the  length  of  the  cylinder.  Thus,  let  the  piston  of  a  hydraulic  press  be  10 
inches  in  diameter,  and  the  pressure  300  tons  net;  then  the  pressure  per  square  inch  of  piston  will  be 
300  tons  divided  by  the  number  of  square  inches  in  the  piston,  or  '-'V'-:" V  =  ?.689  lbs.  The  pres- 
sure  per  inch  in  length  of  the  cylinder  tending  to  split  or  tear  it  apart  is  equal  to  the  diameter  mul- 
tiplied by  the  pressure  per  square  inch ;  or  in  this  case,  10  x  7039  =  76,390  lbs.,  of  which,  of  course, 
each  side  sustains  one-half. 

An  English  rule  for  the  construction  of  cast-iron  cylinders  is  to  make  the  thickness  of  metal  equal 
to  the  interior  radius  of  the  cylinder,  and  to  determine  the  entire  pressure  in  tons.  When  the  diame- 
ter of  the  cylinder  is  given,  the  following  simple  rule  is  used  :  Multiply  the  Bquare  of  the  diameter 
in  inches  by  th3  constant  number  2.9186,  and  the  product  will  be  the  pressure  in  tons.  And  again, 
when  the  pressure  in  tons  is  given,  the  diameter  of  the  cylinder  may  be  determined  by  reversingthe 
process,  or  by  the  following  rule:  Divide  the  given  pressure  in  tons  by  the  constant  number  2.9186, 
and  extinct  the  Bquare  root  of  the  quotient  for  the  diameter  of  the  cylinder  in  inches. 

Example. — The  diameter  of  the  cylinder  in  a  hydrostatic  press  is  10  inches;  what  is  its  power,  or 
what  pressure  does  it  transmit  ?  Here,  by  the  first  rule  above,  we  have  P=  10!  x  2.9186  =  291.86 

Example. — What  is  the  diameter,  and  what  the  thickness  of  metal,  in  a  press  of  300  tons  power? 
By  the  second  rule  above,  we  have  Z>-  =  300  -r-  2.9186  =  102.81  nearly.  Therefore,  by  extracting 
the  square  root,  we  obtain  D  =  |/ 102.81  =  10.13  inches.  Consequently,  the  thickness  of  metal  is, 
t  =  10.13  h-  2  =  5.065  inches. 

Examples  of  mechanical  construction  of  hydraulic  presses  will  be  found  under  Tin - 
The  Hydrostatic  Bellows,  Bhown  in  Fig.  2339,  acts  upon  the  same  principle  as  the  hydrostatic  press; 
the  cover  of  the  bellows,  upon  which  the  weight  is  placed,  performing  the  office  of  the  large  piston, 
while  the  column  of  water  in  the  tall  vertical  pipe  acts  the  part  of  the  small  piston  of  the  press. 
The  hydrostatic  bellows  also  illustrates  the  principle  of  the  hydrostatic  paradox,  for  the  vertical  pipe 
and  bellows  are  virtually  one  vessel,  the  base  of  which  is  the  bottom  of  the  bellows.  The  pressure 
exerted  by  the  liquid  in  the  pipe  upon  the  upper  plate  of  the  bellows  is  received  by  the  lower  plate, 
which  also  has  an  additional  pressure  equal  to  its  distance  below  the  upper  plate;  and  if  the  water 
in  the  pipe  is  ten  times  as  high  as  that  in  the  bellows,  it  follows  that  the  pressure  on  the  bottom 
plate  will  be  ten  times  as  great  as  that  which  would  be  produced  by  the  liquid  contained  within  the 
bellows  itself,  for  that  is  only  equal  to  its  own  weight.  If  a  barrel  of  water  therefore  have  a  tall 
tube  inserted  in  one  head  and  standing  vertically,  a  pressure  may  be  produced  on  its  bottom  several 
thousand  times  that  due  to  the  weight  of  the  water  alone.  In  accordance  with  this  law  of  hydro- 
static pressure,  a  liquid  will  rise  to  the  same  height  in  different  branches  of  the  same  vessel,  whether 
these  branches  be  great  or  small.  Thus,  water  contained  in  the  U-shaped  vessel,  Fig.  2340,  will  rise 
to  the  same  height  in  both  branches,  which  is  an  illustration  of  the  principle  that  the  pressure  of  a 
column  of  liquid  is  in  proportion  to  its  height  and  not  to  its  quantity.  This  principle,  however,  if  it 
is  entitled  to  such  a  name,  proceeds  directfy  from  the  principle  of  Archimedes  that  each  particle  in 
a  liquid  at  the  same  depth  receives  an  equal  pressure  in  all  directions.  If,  however,  one  leg  of  a 
U-shaped  tube  contain  mercury  and  the  other  water,  the  column  of  water  will  stand  13+  times  as  high 
as  that  of  mercury. 

It  follows  from  the  fact  that  a  liquid  presses  equally  upon  equal  areas  of  a  containing  vessel  at  the 
same  depth,  that  if  a  hole  is  made  in  one  side  of  a  vessel,  less  pressure  will  be  exerted  in  the  direc- 
tion of  that  side  ;  and  therefore,  if  the  vessel  is  floated  on  water,  as  in  Fig.  2341,  it  will  be  propelled 
in  the  direction  of  the  arrow.  Barker's  centrifugal  mill,  a  small  model  of  which  is  shown  in  Fig. 
2342,  acts  upon  the  same  principle  of  inequality  of  pressure  on  opposite  sides.  The  propelling  force 
has  been  ascribed  to  the  action  of  the  escaping  liquid  pressing  against  the  atmosphere,  by  which  a. 
corresponding  reaction  is  obtained ;  but  if  the  machine  is  placed  in  a  vacuum,  it  will  rotate  with 
greater  velocity  than  in  the  open  air,  which  proves  that  the  propelling  force  is  the  preponderance  of 
pressure  in  one  direction. 

Laws  of  Pressure.— 1.  The  hydrostatic  pressure  against  equal  areas  of  the  lateral  surfaces  of 



cylindrical  or  prismoidal  vessels,  beginning  at  the  surface  of  the  liquid,  varies  as  the  odd  numbers  1,  3, 
5,  7,  etc.  2.  The  hydrostatic  pressure  against  the  entire  lateral  surfaces  of  cylindrical  or  prismoidal 
vessels  is  proportional  to  the  square  of  the  depth.  The  first  law  is  demonstrated  as  follows :  Hydro- 
static pressure  in  any  direction  at  any  point  in  a  liquid  is  in  proportion  to  the  depth,  a  result  due  to 
the  action  of  gravity ;  therefore  the  mean  pressure  against  any  rectangular  lateral  area  will  be  on  a 



horizontal  line  midway  between  the  upper  and  lower  sides  of  such  area.  The  depth  of  this  line 
proceeding  from  the  surface  of  the  liquid  downward,  varies  as  the  odd  numbers  1,  8,  5,  7,  etc.,  as  will 
be  seen  by  an  inspection  of  the  adjoining  diagram,  Fig.  2343.  The  figures  placed  upon  the  dotted 
lines  in  the  centre  of  the  areas  indicate  the  pressures  upon  those  lines,  and  also  the  proportional 
pressures  against  those  areas.  The  figures  on  the  right  side  of  the  diagram  indicate  the  pressures 
at  points  of  equal  vertical  distances,  while  those  upon  the  left  indicate  the  total  lateral  pressures, 
which  it  will  be  observed  are  the  squares  of  the  number  of  areas  included  ;  by  which  is  demonstrated 
the  second  law,  that  the  total  lateral  pressure  against  rectangular  areas  is  in  proportion  to  the  square 
of  the  depth.  The  weight  of  a  cubic  foot  of  water  is  62.5  lbs. ;  therefore  the  lateral  pressure 
against  a  surface  of  a  square  foot,  whose  upper  side  is  in  the  surface  of  the  liquid,  is  31.25  lbs. 
From  this  it  is  easy  to  ascertain  the  pressure  against  a  square  foot,  or  any  area,  at  any  depth  below 
the  surface.  Simply  multiplying  the  number  of  feet  below  the  surface  by  2  and  subtracting  1,  mul- 
tiplying the  remainder  by  31.25  and  this  product  by  the  number  of  horizontal  feet,  will  give  the 
pressure  of  a  stratum  of  water  a  foot  deep,  at  any  depth  below  the  surface  and  of  any  length.  To 
ascertain  the  entire  pressure  against  the  sides  of  a  vertical  cylindrical  or  prismoidal  vessel,  square 
the  depth  of  the  liquid  in  feet  or  inches,  and  multiply  this  by  the  lateral  pressure  against  an  upper 
vertical  square  foot  or  inch,  as  the  case  may  be,  remembering  that  the  weight  of  a  cubic  inch  of 
water  is  .5792  of  an  ounce,  and  therefore  that  the  pressure  against  an  upper  lateral  side  is  .2896  of 
an  ounce. 

Example. — What  is  the  total  pressure  exerted  against  the  sides  of  a  cylindrical  pipe  60  ft.  high 
and  2  in.  in  diameter?  602  x  31.25  =  112,500.  The  diameter  of  the  pipe  being  2  in.,  the  circum- 
ference of  the  inner  surface  is  2  x  3.141592  (the  constant  ratio)  =  6.283184  in.,  or  B-SAfyja.  0f  a 
foot.  Therefore,  112,500  x  s^a/si  =  58,904.92  lbs.,  or  29.45  tons.  The  lateral  pressure  on  the 
lower  foot  would  be  (60  x  2)  —  1  =  119  x  31.25  x  ^ax&i  =  1,959.64  lbs.,  or  a  little  less  than  one 

In  the  construction  of  walls  for  resisting  only  the  hydrostatic  pressure  of  water,  as  that  pressure  is 
in  proportion  to  the  depth,  the  strength  of  the  wall  should  be  in  the  same  proportion.  If  strength 
were  not  given  to  the  lower  layers  by  superincumbent  pressure,  the  inclination  of  the  slope  should  be 
45° ;  but  in  consequence  of  this  pressure  it  may  be  less,  varying  with  the  materials  and  their  man- 
ner of  being  put  together.  In  the  construction  of  dams  or  barrages  the  varying  circumstances  of 
cases  allow  of  the  display  of  a  good  deal  of  engineering  skill.  A  barrage  suitable  for  restraining  a 
body  of  water  which  is  never  strongly  moved  in  a  lateral  direction  against  it,  as  at  the  outlet  of  a 
canal  or  a  reservoir  fed  by  an  insignificant  stream,  would  not  be  adapted  to  a  mountain  torrent, 
where  the  surface  of  the  reservoir  can  scarcely  ever  be  large  enough  to  prevent,  by  the  inertia 
offered  by  a  large  mass  of  water,  the  walls  from  being  subjected  to  a  strong  lateral  force  from  the 
action  of  the  current.  Under  such  circumstances  it  is  usual  to  give  a  curved  surface  to  the  facings, 
in  a  vertical  as  well  as  in  a  horizontal  direction  ;  the  curves  in  both  directions  being  calculated  from 
the  following  elements  :  1,  the  ascertained  hydrostatic  pressure ;  2,  the  nature  of  the  materials,  such 
as  the  weight  of  stone  and  tenacity  of  the  hydraulic  cement  used  ;  and  3,  an  estimate  of  the  maxi- 
mum force  of  flowing  water  which  may  at  any  time  be  brought  against  the  structure  during  a  freshet. 
This  force,  it  will  readily  be  seen,  will  have  a  different  direction  and  a  different  point  of  application 
in  different  cases,  depending  upon  the  depth  and  extent  of  the  reservoir.  The  top  of  the  dam  is 
therefore  given  a  greater  horizontal  section  than  would  be  called  for  if  hydrostatic  pressure  alone 
had  to  be  opposed.  The  hydrostatic  pressure  at  any  point  against  the  surface  of  a  containing  vessel 
is  the  resultant  of  all  the  forces  collected  at  that  point,  and  is  therefore  at  right  angles  to  that 
surface.  In  a  cylindrical  or  spherical  vessel  these  resultants  are  in  the  direction  of  the  radii,  and  in 
the  sphere  vary  in  direction  at  every  point. 

Centre  of  Pressure. — The  centre  of  pressure  is  that  point  in  a  surface  about  which  all  the  resultant 
pressures  are  balanced.  The  cases  are  innumerable,  and  often  require  elaborate  mathematical  inves- 
tigation.    The  simplest  case  and  its  general  application  only  will  be  considered  here,  viz.,  that  of 



the  centre  of  pressure  against  a  side  of  a  rectangular  vessel.  Let  any  base  in  the  triangle  A  B  C, 
Fig.  2344,  represent  the  pressure  at  B ;  then  will  BE  represent  the  pressure  at  E,  and  all  lines 
parallel  to  it  will  represent  the  pressures  at  corresponding  heights.  The  finding  of  the  centre  of 
pressure  now  consists  in  finding  the  centre  of  gravity  of  the  triangle  ABC,  which  will  be  at  77,  the 
intersection  of  the  bisecting  lines  E  t '  and  I)  B,  and  at  one-third  the  height  of  the  side  A  B  ;  con- 
sequently the  centre  of  hydrostatic  pressure  against  the  rectangular  side  A  B  is  at  G,  one-third  the 
distance  from  the  bottom  to  the  surface  of  the  liquid.  The  average  intensity  of  pressure  against 
A  B  being  at  E,  one-half  the  depth  of  A  B,  therefore  the  total  pressure  on  the  rectangular  side  A  B 
will  be  the  same  as  if  it  formed  the  bottom  of  the  vessel  and  was  pressed  upon  by  a  column  of  water 
of  half  the  depth  of  A  B.  In  general,  the  total  pressure  on  any  surface,  plain  or  curved,  is  equal  to 
the  weight  of  a  liquid  column  whose  base  is  equal  to  that  surface,  and  whose  height  is  the  distance 
of  the  centre  of  gravity  of  the  surface  from  the  surface  of  the  liquid. 

Principle  of  Archimedes. — A  solid  immersed  in  liquid  loses  an  amount  of  weight  equal  to  that  of 
the  liquid  it  displaces.  This  is  called  the  principle  of  Archimedes,  and  is  demonstrated  as  follows: 
Let  a  b,  Fig.  2345,  be  a  solid  immersed  in  a  liquid.  The  vertical  section  cd  will  be  pressed  down- 
ward by  a  force  equal  to  the  weight  of  the  column  of  water  cc,  and  it  will  be  pressed  upward  by  a 
force  equal  to  that  exerted  by  a  column  of  water  equal  toed;  therefore  the  upward  or  buoyant 
pressure  exceeds  the  downward  pressure  by  the  weight  of  a  column  of  water  equal  to  the  section  cd. 
Now,  this  section  also  exerts  a  downward  pressure;  and  if  the  body  is  denser  than  the  liquid,  the 
downward  pressure  will  be  greater  than  the  excess  of  the  upward  pressure  <>t  the  liquid,  and  the 
body  will  sink  if  not  supported  ;  but  if  the  body  is  less  dense  than  the  liquid,  the  downward  pressure 
of  the  column  <  d  will  be  less  than  the  upward  pressure  exerted  against  it,  and  the  body  will  float. 

This  principle  may  be  experimentally  demonstrated  by  the  hydrostatic  balance,  Fig.  2346.  From 
a  balance,  b,  is  suspended  a  cylindrical  vessel,  o,  from  which  again  is  suspended  a  solid  cylinder,  c, 

23 13. 





— / — 



—    3-  ■- 






-7    " 


—9  — - 











— = 



-  - 

2:;  IS 


[I     - 



',        -r_ 


which  is  of  such  bulk  and  dimensions  as  just  to  fill  the  vessel  a  when  introduced.  The  whole  system 
is  first  balanced  by  weights  at  the  other  end  of  the  beam,  and  then  c  is  immersed  in  water.  The 
equilibrium  will  be  destroyed,  and  that  the  body  c  loses  a  portion  of  its  weight  equal  to  that  of  an 
equal  bulk  of  water  is  proved  by  filling  the  vessel  a  with  water,  when  the  equilibrium  of  the  balance 
will  be  restored.  It  is  by  mean's  of  a  similar  apparatus  that  the  specific  gravities  of  solids  are  ascer- 
tained (see  Gravity,  Specific)  ;  and  upon  the  principles  already  laid  down  hydrometers,  or  instru- 
ments for  ascertaining  the  specific  gravity  of  liquids,  are  constructed. 

Stability  of  Floating  Bodies. — There  are  certain  points  to  be  observed  in  determining  the  stability 
of  floating  bodies;  these  are:  1,  the  centre  of  gravity  of  the  floating  body;  2,  the  centre  of  buoy- 
ancy ;  and  3,  the  metacentre.  When  a  body  floats  upon  water  it  is  acted  on  by  two  forces :  1,  its 
own  weight,  acting  vertically  downward  through  its  centre  of  gravity;  2,  the  resultant  force  produced 
by  the  upward  pressure  of  the  liquid,  which  acts  through  the  centre  of  gravity  of  the  fluid  that  is 
displaced,  which  point  is  called  the  centre  of  buoyancy  of  the  body.  It  follows,  therefore,  that 
these  two  points,  the  centre  of  gravity  and  the  centre  of  buoyancy,  must  be  in  the  same  vertical  line 
for  the  body  to  be  in  a  state  of  equilibrium ;  for  otherwise  the  two  forces,  one  acting  downward  and 
the  other  upward,  would  form  a  couple  which  would  cause  the  body  to  turn.  When  these  two  cen- 
tres are  in  the  same  vertical  line,  but  the  centre  of  gravity  is  above,  the  body,  except  in  some  eases 
to  be  noted  presently,  is  in  a  state  of  unstable  equilibrium ;  but  when  the  centre  of  gravity  is 
beneath,  the  body  is  in  a  state  of  stable  equilibrium.  If  a  body  is  floating  in  a  liquid  and  is  entirely 
immersed,  it  will  not  come  to  a  state  of  stable  equilibrium  until  the  centre  of  gravity  is  vertically 
below  the  centre  of  buoyancy.  This  is  shown  in  Fig.  2347,  in  the  case  of  bodies  which  are  less 
dense  at  one  end  than  at  the  other,  where  B  and  B'  are  the  centres  of  buoyancy  and  G  and  G'  those 
of  gravity. 

But  in  many  cases,  when  a  body  is  only  partially  immersed,  the  centre  of  gravity  may  be  above 
that  of  buoyancy,  and  yet  the  action  of  turning  cannot  take  place,  so  that  a  condition  of  stable 



When  the  metacentre  is  above  the  centre 



equilibrium  will  be  attained  under  these  circumstances.  If  a  flat  body,  such  as  a  light  wooden 
plank  is  placed  in  water,  it  will  float,  and  a  portion  will  be  above  the  surface,  as  shown  in  Fig.  2348 ; 
and  therefore  if  the  centre  of  gravity  is  not  below  the  centre  of  volume,  it  will  be  above  the  centre 
of  buoyancy,  and  yet  the  body  will  be  in  a  state  of  stable  equilibrium.  For  if  it  be  tipped  as  repre- 
sented in  Fig  2349,  the  centre  of  buoyancy  will  be  brought  to  the  position  JB',  on  the  depressed  side 
of  the  vertical  passing  through  the  centre  of  gravity,  and  this  will  cause  the  body  to  return  to  its 
former  position.  But  if  the  body  has  such  a  shape  that  when  it  is  displaced  the  centre  of  buoyancy 
is  brought  to  that  side  of  the  vertical  passing  through  the  centre  of  gravity,  which  is  elevated  as 
represented  in  Fig.  2350,  then  the  body  will  turn  over.  When  the  body  is  in  the  new  position,  a  vertical 
drawn  through  the  changed  position  of  the  centre  of  buoyancy  will  intersect  the  line  which  in  the 
first  position  passed  vertically  through  the  centre  of  gravity,  and  this  point  of  intersection  is  called 
the  metacentre,  represented  at  M  in  Figs.  2350  and  2351.  ' 
of  gravity,  as  in  Fig.  2351,  the  body  will  tend, 
by  the  action  of  the  centre  of  buoyancy,  to  re-  2348. 

turn  to  its  former  position ;  but  when  it  is  be- 
low, as  in  Fig.  2350,  the  action  of  the  centre  of 
buoyancy,  being  upward  on  the  elevated  side, 
will  tend  to  turn  the  body  over.  Its  proper 
place,  therefore,  as  its  name  would  indicate,  is 
above  the  centre  of  gravity,  but  it  cannot  be  a 
fixed  point.  In  all  well-built  ships,  however,  its 
position  is  pretty  nearly  constant  for  all  inclina- 
tions. For  example,  in  Fig.  2351,  as  long  as 
increase  of  inclination  of  the  vessel  carried  the 
centre  of  buoyancy  B  to  the  left,  the  point  M 
might  remain  at  nearly  the  same  distance  from 
67,  because  it  would  also  move  to  the  left.  But 
if  the  inclination  of  the  vessel  in  the  same  direc- 
tion carried  the  centre  of  buoyancy  to  the  right, 
the  height  of  the  metacentre  M  would  diminish  until  it  would  be  in  67,  when  the  equilibrium  would 
be  indifferent,  and  at  last  below  G,  when  the  ship  would  turn  over.  It  is  desirable  to  have  the 
metacentre  as  far  as  possible  above  the  centre  of  gravity ;  and  this  condition  is  secured  by  bringing 
the  centre  of  gravity  to  the  lowest  practicable  point,  by  loading  the  ship  with  the  heaviest  part  of 
the  cargo  nearest  the  keel,  or  by  employing  ballast. 

ICE-HARVESTING  APPARATUS.  Ice-cutting,  as  practiced  on  the  lakes  and  rivers  of  this 
country,  is  a  process  essentially  American.  The  season  during  which  ice  can  be  gathered  is  (at  least 
in  the  Eastern  States)  so  brief  that  the  utmost  activity  is  required  to  obtain  the  supply  necessary  for 
home  consumption,  irrespective  of  the  demands  of  our  large  export  trade,  which  in  1S76  amounted 
to  over  60,000  tons,  representing  $200,000  in  value.  Ice  has  been  a  commodity  only  since  1825.  In 
1876  the  amount  required  for  home  consumption  and  harvested  was  over  2,000,000  tons,  requiring  a 
force  of  10,000  men  and  4,000  horses. 

Harvesting. — When  a  favorable  time  comes  for  gathering  the  ice,  there  is  a  scene  of  great  activity 
in  the  vicinity  of  the  storing-houses.  A  field  is  laid  out  varying  according  to  the  facilities  for  gather- 
ing. On  the  Hudson  River  in  New  York,  and  the  Kennebec  River  in  Maine,  from  which  immense 
quantities  are  taken,  the  first  operation  is  the  removal  of  any  loose  snow.     This  is  accomplished  by 



means  of  the  V-shaped  plough,  and  also  what  is  known  as  the  fire-board  scraper,  Fig.  2352.  The 
snow  now  being  removed  and  the  "  field "  clear,  the  next  operation  is  to  mark  out  a  line  for  a 
machine  known  as  the  "  marker."  This  is  generally  accomplished  by  stretching  over  the  ice  a  line 
half  an  inch  thick  and  several  hundred  feet  long,  which  is  used  as  a  guide  in  making  the  first  cut. 
The  marker  generally  used  consists  of  a  wrought-iron  back  with  head-piece  and  handle-sockets,  all  in 
one.  Into  the  back  are  set  eleven  cutting  teeth  of  cast  steel,  half  an  inch  thick,  and  varying  in 
length  from  half  an  inch  in  the  first  tooth  to  3  inches  in  the  last,  clear  of  the  back.  Each  tooth  has 
2  inches  insertion,  and  they  are  secured  in  position  by  two  wrought-iron  bolts.  Immediately  in 
front  of  the  first  tooth  is  a  small  piece  of  steel  a  quarter  of  an  inch  shorter  than  the  first  tooth.  Its 
purpose  is  to  remove  loose  ice,  stones,  etc.,  from  the  path  of  the  marker.     Each  tooth  cuts  a  quarter 



of  an  inch,  the  full  depth  being  3  inches ;  the  cutting  depth  can  be  regulated  by  the  adjustable 
guide  at  the  heel  of  the  marker.  Attached  to  the  back  of  the  marker  by  a  hinge-joint  and  bolts  is 
the  swing-guide,  made  of  cast-steel,  designed  to  regulate  the  size  of  the  cake  to  be  cut.  Each  marker 
has  two  such  guides,  of  22  and  32  inches.  The  guide  is  steadied  by  a  bar  extending  to  the  stiffcning- 
rod  of  the  handle,  and  also  used  to  raise  the  guide  in  case  an  obstruction  is  met. 

The  marker  follows  with  its  guide  the  line  first  laid  out.  When  the  end  of  the  line  is  reached,  the 
guide  is  reversed  and  set  to  run  in  the  groove  just  made,  and  this  process  is  repeated  at  a  distance  of 
22  inches  between  each  cut  until  the  whole  field  is  marked  off  in  parallel  lines. 

The  lee  Plane,  represented  in  Fig.  2353,  is  used  to  cut  off  snow-ice  and  dirty  ice.     It  is  made  of 

cast-iron,  is  22  inches  wide,  and  is  quite  heavy.     After  marking  the  ice  to  a  uniform  depth  with  a 

marker,  the  sides  of  the  plane  run  upon  the  bottom  of  these  gi ves,  and  the  knife  can  be  set  to  cut 

off  any  thickness  up  to  about  8  inches,  as  desired.  The  amount  cut  off  is  regulated  by  setting  the 
knife  by  means  of  the  set-screws  on  the  sides ;  these  should  be  securely  screwed  into  their  seats 
before  using  the  plane.  The  weight  of  the  driver  keeps  the  plane  steady  in  the  grooves.  When  the 
plane  has  rendered  the  ice  smooth,  the  marker,  with  its  guide  changed  to  32  inches,  crosses  the  par- 
allel lines  at  right  angles,  and  continues  until  the  field  is  marked  off  in  blocks  22  by  32  inches.     The 




h    h 

plough  is  now  used  to  finish  the  cutting,  which  is  generally  required  to  be  one-half  the  thickness  of 
the  ice,  but  varies  according  as  the  ice  is  soft  or  very  thick. 

Ice-Ploughs. — Ice-ploughs  are  designed  to  finish  the  work  begun  by  the  markers,  and  they  are 
graded  to  follow  each  other  according  to  the  thickness  of  the  ice  to  be  harvested.  The  cutting  is  done 
by  means  of  a  series  of  teeth,  each  one  of  which  varies  slightly  in  length  from  the  rest,  the  shortest 
being  at  the  front  of  the  row.  Each  of  these  teeth  will  cut  about  a  quarter  of  an  inch  of  ice,  so  that 
a  plough  with  8  teeth  will  go  through  about  2  inches  each  time  it  passes  along  the  grooves.  Ice-ploughs 
are  made  either  with  or  without  the  swinging  or  stationary  guide,  these  being  required  only  when  the 
marker  is  dispensed  with.  Fig.  2354  represents  the  form  of  ice-plough  made  by  the  Knickerbocker 
Ice  Company  of  Philadelphia  (to  which  corporation  we  are  indebted  for  much  information  and  many 
of  the  engravings  presented  in  this  article).     The  implement  here  depicted  is  strongly  made  of  cast- 



steel.  Fig.  2355  shows  a  hand-plough,  used  for  drawing  the  first  straight  line  on  the  ice  for  the 
marker  or  plough  to  follow.  It  is  also  convenient  for  reopening  short  grooves  which  have  been  frozen, 
for  finishing  the  ends  of  grooves,  or  for  marking  large  blocks  intended  to  be  cut  into  two  or  more 
cakes  when  taken  from  the  ice-house. 

After  the  plough  has  cut  the  ice  to  proper  depth,  the  ice-saiv,  Fig.  2356,  is  used  to  open  the  channel 
through  which  the  blocks  are  to  pass  to  the  hoisting  machine,  or  to  cut  them  to  the  desired  size.  This 
implement  varies  in  length  from  4  to  5  feet.  The  first  row  of  ice-blocks,  after  being  sawed,  are  either 
pushed  under  or  hauled  out.    Afterward  the  blocks  are  separated  by  the  tools  represented  in  Fig.  2357. 

Ice  Tools. — A,  Fig.  2357,  is  the  ice-hook,  used  for  storing  ice  in  houses,  towing  it  in  the  field,  or 
handling  it  on  the  platforms  or  cars.  The  handle  varies  from  4  to  16  feet  in  length.  B  is  a  fork  split- 
ting-bar, for  splitting  the  sheets  as  they  pass  along  the  channels  to  the  elevator.  The  teeth  split  the 
ice  evenly,  and  for  this  reason  this  implement  is  often  preferred  to  the  single  broad  blade.  C  is  a 
grooving-bar,  supplied  with  a  broad,  blunt  blade  at  one  end,  which  is  used  to  insert  in  the  grooves 
made  by  the  plough  and  to  break  off  the  ice  from  the  field  into  sheets  ;  at  the  opposite  end  there  is 
a  sharp  blade  like  a  chisel,  which  is  employed  only  when  the  groove  has  been  frozen  over.    D  is  a 




channel  hook-bar,  or  chisel  and  hook  combined.  This,  when  attached  to  a  long  wooden  handle,  is 
very  convenient  for  drawing  the  ice  near  enough  with  the  hook  to  split  the  sheets  and  single  cakes 
with  the  chisel  part  of  the  bar.  E  is  a  splitting-bar,  used  to  split  large  sheets  into  single  blocks  as 
they  are  floated  along  the  channels  to  the  ice-house.  The  ring  is  desirable,  as  it  prevents  the  bar 
from  slipping  through  the  hands  in  wet  or  very  severe  weather.  F  is  a  calking-bar,  used  for  packing 
the  grooves  made  by  the  plough  at  the  sides  and  ends  of  the  sheets,  and  thus  preventing  the  water 
from  flowing  into  the  grooves  and  freezing  the  blocks  together  again  while  they  are  being  floated  down 
the  channel  to  the  ice-house.  G  is  a  chisel  or  raising-bar  for  separating  the  cakes ;  and  H  is  another 
form  of  splitting-bar  used  for  both  separating  and  splitting  the  cakes. 

Grapples  are  represented  in  Figs.  2358  and  2359.     These  are  chiefly  used  to  draw  ice  up  an  inclined 
plane  where  there  is  no  other  elevating  machinery  for  filling  ice-houses.     That  represented  in  Fig. 



2358  is  a  much  heavier  and  stronger  implement  than  that  shown  in  Fig.  2359,  and  is  generally  fur- 
nished with  a  stationary  plough-handle. 

Elevating  and  Storing  Ice. — Various  means  are  employed  for  elevating  the  blocks  of  ice  into  the 
storehouses.     Dealers  who  harvest  small  crops,  ranging  from  4,000  to  8,000  tons  per  season,  neces- 
sarily use  devices  of  the  simplest  kind.     Tongs,  such  as  are  represented  in  Figs.  2360  and  2361,  are 



most  commonly  employed.  These  are  made  of  well-tempered  steel  The  form  shown  in  Fig.  2361  is 
finished  with  adjustable  joints,  with  three  teeth  in  the  plate,  which  press  firmly  against  the  sides  of 
the  ice      Two  pairs  of  tongs  can  be  worked  with  one  horse. 

lleGiys  or  ?W/omS,  of  the  shape  shown  in  Fig.  2362,  are  often  used  instead  of  tongs.  The  block 
ia  pnsilv  floated  unon  the  eis,  which  is  then  hoisted. 

Where  large  amounts  of  ice  are  harvested,  elevators  of  special  construction  are  employed.  Of 
these  there  are  two  classes  :  the  ice-screw  and  the  inclined  plane  or  endless  chain 

The  Ice-Screw  Elevator,  made  by  the  Knickerbocker  Ice  Company  of  Philadelphia,  consists  of  a 
large  helix  of  wrought-iron  wound  about  a  wooden  stem.     The  latter  is  rotated  by  spur-gearmg,  con- 

nected by  belting  with  the  horse-power.  The  ice,  being  floated  upon  the  helix,  is  caused  by  the  rota- 
tion of  the  latter  to  ascend  and  finally  to  pass  off  by  a  chute.  By  reversing  the  motion,  the  ice  can 
be  lowered  from  the  building  as  rapidly  as  it  can  be  elevated,  the  weight  of  the  ice  furnishing  the 
power.     A  simple  brake  is  required  to  prevent  the  screw  from  revolving  too  rapidly,  and  to  stop  it 

™hTh?End£s  Cham  Elevator  is  represented  in  operation  in  Fig.  2363.  The  apparatus,  as  made  by  the 
Knickerbocker  Ice  Companv  of  Philadelphia,  consists  of  an  endless  chain,  which  runs  along  a  load- 
ing platform  to  the  doorways  of  the  ice-house  or  series  of  ice-houses,  as  the  case  may  be.  At .inter- 
vals on  the  wharf  side  of  this  platform  are  hoisting-ways,  by  means  of  which  the  ice  is .taken  from 
the  vessel's  hold  and  deposited  on  the  chutes.     The  latter  are  elevated  so  as  to  give  the  ice  sufficient 



motion  to  carry  it  gently  to  its  place  on  the  chain,  when  it  is  conveyed  along  the  platform,  until  it 
reaches  the  point  where  wagons  are  ready  to  receive  it,  or  is  conducted  up  into  the  ice-houses,  should 
it  be  intended  for  storage.  The  rear  portion  of  the  platform  is  supplied  with  a  simple  adjusting 
apparatus,  by  which  the  runs  can  be  elevated  or  depressed,  as  the  ice  may  be  wanted  at  the  top  of  the 
ice-house  or  on  a  level  with  the  platform.  When  the  machine  is  needed  for  loading  from  the  house 
instead  of  from  the  vessel,  the  motion  is  simply  reversed,  when  the  ice  is  brought  down  the  inclined 
plane  and  along  the  platform  to  the  wagons  or  cars,  as  may  be  required.  By  the  aid  of  one  of  these 
machines,  1,000  tons  of  ice  daily  can  readily  be  removed  from  the  vessel  to  the  ice-house,  or  from  the 
latter  to  cars  or  wagons,  and  with  regularity  and  ease. 

Two  forms  of  this  device  are  made,  one  "  overshot "  and  one  "  undershot,"  the  latter  feeding  the 
ice  under  the  shaft  by  reversing  the  motion  of  the  chain.  The  advantages  of  this  last  device  are,  that 
the  elevator  can  be  used  in  very  shallow  water,  and  can  be  adapted  to  any  ice-house,  to  an  incline  of 
any  grade,  and,  by  putting  in  an  extra  pair  of  water-wheels,  to  any  angle.  It  also  requires  less  chain 
than  the  overshot  machine. 

The  Gifford  Elevator,  constructed  by  Gifford  Brothers  of  Hudson,  N.Y.,  is  shown  in  Fig.  2364,  which 
represents  a  sectional  view  of  the  "  incline,"  two  chain-wheels,  and  the  friction-gearing  at  the  top  of 
the  house.  An  elevator  is  used  singly  for  a  5-  or  10-ton  house,  or  8  or  10  of  them  for  60-  and  80-ton 
houses  may  be  connected  by  a  line  of  3£-  or  4-inch  shafting.     The  line  of  shafting  is  situated  4  or  5 

feet  above  the  plate,  and  about  8  feet  from  the  front  of  the  house, 
and  is  driven  by  an  inclined  line  of  shafting  and  bevel-gearing. 
The  engine  and  line-shaft  may  run  continuously,  but  the  elevators 
are  operated  independently  of  each  other.    An  "incline"  or  frame 
extends  from  the  plate  to  the  water-line  or  into  the  water.     Two 
timbers,  4  by  10  inches,  running  parallel  to  each  other,  extend  its 
length.     Inside  of  each  of  these,  and  running  in  the  same  direc- 
tion, are  joists,  bolted  fast,  on  which  the  chain  rides.     Under  the 
timbers,  at  distances  of  2  feet,  are 
cross-joists  over  which  are  laid  light 
strips  2-£  by  H  inches.     The  main 
elevator-shaft  is  provided  with  fric- 
tion-wheels having  V-shaped  grooves 
on  their  sides.  These  drive  two  wheels 
en  another  shaft,  which,  by  means  of 
teeth  on  their  periphery,  carry  end- 
less chains,  one  on  each  side  of  the 

incline.  These  chains  pass  down  and  over  two  wheels  in  the  water,  and  are  connected  by  bars  of 
oak  (4  by  4)  placed  6  feet  apart.  The  bars  catch  and  carry  up  one  or  two  cakes  of  ice,  which  the 
"  feeder  "  shoves  in.  The  incline  is  fitted  with  openings  in  its  framework,  at  various  distances, 
through  which  the  ice  falls  upon  a  "  run,"  on  which  it  slides  by  its  own  gravity  to  the  centre  of  the 
room  where  it  is  "  placed."  A  space  of  2  inches  is  left  around  each  cake.  The  room  being  filled 
to  the  height  of  the  run,  the  opening  in  the  incline  is  closed  and  the  ice  is  carried  to  the  next  open- 
ing above,  and  so  on  till  the  house  is  filled.  Should  there  be  any  obstruction,  the  elevator  tender 
lets  go  the  lever,  the  friction-gears  are  thrown  apart,  and,  as  the  pinion  turns  loosely  on  the  shaft, 
it  fails  to  drive  the  chain-wheels,  and  the  chain  is  stopped  instantly,  and  prevented  from  slipping  by 
a  heavy  positive  brake  acting  on  the  cogs  of  the  chain-wheel.  This  elevator  is  claimed  to  have  a 
capacity  for  raising  two  cakes  of  24-inch  ice  per  bar,  or  720  tons  per  hour,  with  a  chain-speed  of 
120  feet  a  minute. 

Storing-Houses. — The  buildings  used  for  the  storage  of  ice  are  not  constructed  according  to  any 
generally  recognized  plan.  The  walls  are  usually  composed  of  a  substance  which  is  a  non-conductor 
of  heat.  Both  brick  and  wood  are  used  in  their  construction,  each  having  its  advocates.  Those  who 
favor  brick  state  that  ice  keeps  best  where  the  walls  are  double,  with  intervening  dead-air  spaces. 
Those  who  prefer  wood  object  to  brick  on  the  ground  that,  the  outer  wall  being  heated,  the  air 
between  is  also  heated,  and  that  practically  the  greatest  waste  is  in  the  immediate  vicinity  of  the 
walls,  for  a  space  often  of  3  feet  on  all  sides.  In  building  with  wood  heavy  joists  are  used,  sheathed 
inside  and  out  with  1-inch  matched  boards,  the  intervening  distance  of  12  inches  being  well  packed 
with  saw-dust  or  spent  tan-bark.  Sometimes  the  walls  are  triple  or  quadruple.  Some  houses  are 
built  in  stories,  with  sluiceways  to  carry  off  the  melted  ice.  These  buildings,  however,  have  been 
found  to  waste  more  rapidly  than  where  the  entire  space  between  walls  is  filled  with  solid  ice.  The 
wooden  buildings,  being  the  cheaper  and  more  economical,  are  generally  used,  and  are  constructed 
from  100  to  400  feet  front,  100  to  200  feet  deep,  and  35  to  45  feet  high,  and  divided  into  rooms  50 
by  100  feet,  separated  by  thick  partitions,  which  have  an  open  door  from  roof  to  floor,  capable  of 
being  closed  as  the  room  is  filled.  The  capacity  can  be  calculated  from  the  fact  that  a  cake  10  inches 
thick,  measuring  22  by  32  inches,  weighs  about  250  lbs.  The  net  waste  in  a  room  90  by  60  feet,  and 
35  feet  high,  has  been  found  to  be  5  feet  on  top  and  3  feet  on  the  south  side,  the  gross  weight  of  ice 
in  the  building  being  about  3,500  tons. 

Some  of  the  buildings  are  fitted  with  ventilators  of  various  patterns  and  styles ;  but  experience 


shows  that  the  old  cupola  form  is  as  good  as  any.  The  floor  is  generally  the  ground  upon  which  the 
house  is  built,  having  a  slope  of  6  inches  from  the  centre,  the  drainage  being  allowed  to  work  its  way 
under  the  foundation  timbers. 

The  net  cost  of  harvesting  on  the  Hudson  River  is  from  10  to  15  cents  per  ton.  G.  H.  B. 

ICE-MAKING  MACHINERY.  An  economical  means  of  freezing  water  is  a  fruitful  source  of 
profit,  for  the  manufacture  of  ice  serves  not  only  the  purpose  of  enhancing  our  bodily  comfort  in 
summer,  but  also  for  rapidly  cooling  large  volumes  of  liquid,  as  in  the  operation  of  brewing  and 
other  industrial  processes,  and  for  the  better  preservation  of  animal  food  in  seasons  and  climates 
which  hasten  putrefactive  changes.  The  difficulty  experienced  in  freezing  water  is  due  to  the  very 
large  amount  of  heat  it  must  lose,  first,  in  being  lowered  to  the  temperature  of  32°  F.,  and  secondly, 
in  being  changed  from  liquid  water  at  32°  F.  to  solid  ice  at  the  same  temperature.  The  first  quan- 
tity is  called  its  specific  heat,  and  the  second  is  its  latent  heat.  These  quantities  are  greater  for 
water  than  for  any  other  substance ;  hence  the  cooling  power  of  ice  is  greater  for  any  given  tempera- 
ture than  that  of  any  other  body,  and  the  cooling  power  of  water  is  greater  than  that  of  any  gas  or 
liquid.  Faraday  calculated  tluit  the  heat  absorbed  during  the  conversion  of  a  cube  of  solid  ice 
measuring  3  feet  in  the  length  of  one  side  into  liquid  water  without  undergoing  any  rise  of  tempera- 
ture, would  require  the  combustion  of  a  bushel  of  coal  for  its  artificial  production.  It  is  evident 
from  these  statements  that,  in  order  to  cool  a  quantity  of  heated  air  or  water  down  to  a  moderate 
temperature,  a  large  supply  of  water  is  the  best  medium,  not  only  on  account  of  its  cheapness  and 
abundance,  but  because  of  its  great  capacity  for  heat.  When  any  elastic  fluid  is  compressed,  it 
becomes  hot,  and  if  it  then  be  cooled  down  to  its  original  temperature  and  be  expanded,  it  is  ren- 
dered as  many  degrees  colder  by  its  rarefaction  as  it  was  heated  by  its  condensation ;  hence  we  have 
here  a  means  of  producing  low  temperatures.  On  the  other  hand,  we  can  ignite  tinder  by  the  heat 
evolved  in  the  compression  of  air  in  a  glass  cylinder  ;  and  by  the  exhaustion  of  the  air  in  a  bell-jar 
the  temperature  may  be  reduced  so  that  the  moisture  it  contains  is  deposited  as  a  mist. 

By  the  extremely  rapid  expansion  of  a  liquefied  gas  when  pressure  is  removed,  or  of  a  volatile 
liquid  when  its  evaporation  is  hastened  bv  mechanical  means,  we  obtain  the  most  effective  cooling 
powers.  The  familiar  experiment  of  freezing  water  or  mercury  in  a  red-hot  dish  is  effected  by  the 
enormous  expansion  of  liquefied  sulphurous  acid  or  solidified  carbonic  acid,  which  substances  regain 
the  heat  they  lost  when  undergoing  the  change  of  liquefaction  or  solidification.  By  similar  means 
Messrs.  Pictct  and  Cailletet  have  succeeded  in  liquefying  and  even  solidifying  the  permanent  gases. 
To  liquefy  oxygen,  M.  Pictet  uses  a  conical  shell  containing  700  grammes  of  chlorate  of  potash. 
This  shell  answers  as  a  retort,  and  is  placed  over  a  gas-furnace  or  burner.  The  gas  is  compressed 
into  a  long  curved  iron  tube  fitted  to  the  apex  of  the  shell.  This  tube  is  placed  in  a  long  box  on  a 
table,  and  is  terminated  by  a  pressure-gauge;  the  tube  is  hermetically  closed  during  the  time  the  gas 
is  being  produced  ;  the  compression  is  due,  therefore,  solely  to  the  effect  of  the  chemical  decomposi- 
tion. The  above  tube  is  surrounded  by  a  larger  one  containing  liquid  carbonic  acid,  which,  in  volatil- 
izing under  the  action  of  the  suction-pumps,  produces  a  cold  of  —220°  F.  This  liquid  carbonic  acid 
is  liquefied  in  a  tube  contained  in  a  smaller  box  placed  above  the  first  large  one.  Two  compression- 
pumps  take  the  carbonic  acid  in  a  gaseous  state  from  a  gasometer,  and  compress  it  into  the  tube  con- 
tained in  the  small  box.  This  tube  forms  a  reservoir  of  liquid  carbonic  acid,  and  must  be  made  very 
cold.  It  is  enveloped  by  a  larger  tube  containing  liquid  sulphurous  oxide,  which  is  continually  vapor- 
ized. The  liquid  sulphurous  oxide  is  constantly  provided  from  a  reservoir  or  condenser,  and  the  duty 
of  two  pumps  is  to  exhaust  the  oxide  from  around  the  carbonic  acid  and  compress  the  oxide  again 
into  a  liquid  state  in  the  condenser.  M.  Pictet  found  that  oxygen  was  liquefied  at  —202°  F.  (  — 130° 
C.)  under  a  tension  of  273  atmospheres,  when  carbonic  acid  was  employed,  and  at— 220°  F.  ( — 140° 
C.)  with  a  tension  of  252  atmospheres  when  nitrous  oxide  was  used.  The  maximum  pressure  used 
during  the  experiment  was  525  atmospheres.  For  hydrogen,  a  pressure  of  652  atmospheres  and  a 
cold  of  —220°  F.  were  found  necessary  to  liquefy  it.  In  the  above  experiments  the  solidification  of 
particles  was  made  apparent  by  the  peculiar  sound  of  the  gas  as  it  issued  from  the  tube  when  the 
valve  was  opened,  the  particles  striking  the  floor  with  a  noise  like  that  of  fine  hail.  The  electric  light 
thrown  on  the  jet  showed  a  bright  central  core  of  6olid  matter.  Air  has  also  been  liquefied  by  the 
above  process.  (See  La  Nature,  1877,  1878 ;  Journal  of  the  Franklin  Institute,  ex.,  187,  190,  319 ; 
Scientific  American,  xxxviii.,  147;  Scientific  American  Supplement,  v.,  1883  ;  Engineering,  xxv.,  324.) 

The  performances  of  ice  machines  indicate  remarkable  abstractions  of  heat  in  proportion  to  the 
fuel  consumed.  The  theoretical  considerations  governing  the  freezing  by  expanded  air  are  as  follows : 
The  amount  of  heat  to  be  taken  from  a  pound  of  water  at  60°  to  reduce  it  to  ice  at  32°  is  170  units, 
namely  :  one  pound  of  water  at  60°  to  ice  at  32'  involves  an  abstraction  of  28,  and  between  water  at 
32°  to  ice  at  32°  are  (latent)  142  units.  One  pound  of  air  at  1  atmosphere  and  at  60°  compressed  to 
2  atmospheres  is  heated  116° ;  multiplying  this  by  .238  specific  heat,  we  have  27.6  units  per  pound  of 
air.  Hence  to  freeze  a  pound  of  water  from  60°  requires  (170  -s-  27.6  =  )  6.16  lbs.  of  air,  which  is 
equal  to  81  cubic  feet  of  air  at  1  atmosphere  and  at  60°.  Now  to  compress  1  cubic  foot  of  air  to 
2  atmospheres  requires  1,630  foot-pounds.  Therefore  1,630  x  81  =  132,030  foot-pounds,  or  total 
required  to  compress  81  cubic  feet  to  2  atmospheres.  The  mechanical  equivalent  of  the  unit  of 
heat  (see  Dynamics,  and  Expansion  of  Steam  and  Gases)  is  772  foot-pounds ;  hence  the  170  units 
necessary  to  be  taken  from  a  pound  of  water  in  order  to  freeze  it  required  170  x  772  foot-pounds 
=  131,240  foot-pounds,  which  is  very  nearly  the  amount  we  have  calculated.  The  indicated  horse- 
power being  equal  to  33,000  foot-pounds  per  minute,  one  horse-power  therefore  would  produce 
(33,000  x  60  -T- 132,030  =  )  15  lbs.  of  ice  per  hour.  If  33  per  cent,  be  deducted  for  friction  of  air- 
pumps,  etc.,  and  allowing  5.75  lbs.  of  coal  per  indicated  horse-power,  we  have  (10  -s-  5.75  = )  1.75 
lb.  of  ice  per  pound  of  coal. 

In  ice  machines  wherein  ether,  etc.,  is  evaporated,  the  proportionate  yield  far  exceeds  these  figure*. 
In  the  Siddeley  and  Mackay  machine,  which  will  be  found  described  farther  on,  the  proportion  is  1 



lb.  of  coal  to  8  lbs.  of  ice,  this  having  been  determined  by  over  15  months'  continuous  running.    (See 
Engineering,  xxiii.,  484.) 

The  reason  for  the  more  economical  operation  of  the  compressed-air  machines  is  readily  seen  from 
the  following 

Table  of  Corresponding  Pressures,  Boiling-Points,  and  Volumes  of  Watery  Vapor. 

Inches  of  Mercurial 

Corresponding  Pres- 

Corresponding Approxi- 

Volume of  the  Yapor 

Column  in 

sure  in  Pounds 

mate  Temperature  of 

compared  with 


per  Square  lech. 


the  Water. 




















'     60,000 





















From  this  it  appears  that  as  the  pressure  and  temperature  decrease  the  volume  of  the  vapor 
enormously  increases,  so  that,  at  the  freezing-point  of  water  under  a  pressure  of  nearly  one-tenth  of 
a  pound  per  square  inch,  the  expansion  of  the  watery  vapor  is  more  than  200,000  times  the  bulk 
of  the  liquid.  Consequently  very  active  measures  are  needed  to  dispose  of  this  vapor,  which  other- 
wise would  accumulate  and  by  its  pressure  soon  end  all  further  evaporation  and  subsequent  cooling. 
Hence  the  disadvantage  of  the  vacuum-pumps  acting  alone,  and  the  necessity  of  removing  this  vapor 
by  extraneous  aid.  Air  machines  also  require  large  cylinders  and  air-tight  close-fitting  pistons,  besides 
accurate  fitting  in  the  various  valves.  On  the  other  hand,  they  have  the  advantage  of  requiring  no 
aid  from  chemical  agents,  of  acting  directly  upon  the  air  and  water,  and  of  producing  cold  air,  refrig- 
erating fluids,  or  making  ice  continuously,  as  wished,  with  the  aid  of  fuel  alone.  Perhaps  the  air 
machine  is  the  one  best  suited  for  the  artificial  refrigeration  of  air  apart  from  ice-making,  inasmuch 
as  the  requisite  amount  of  cold  can  be  regulated  with  the  greatest  nicety  by  means  of  a  valve  under 
the  control  of  the  attendant. 

Air  Machines. — The  principal  types  are  as  follows  :  In  the  Windhausen,  Fig.  2365,  A  is  the  com- 
pression and  B  the  expansion  cylinder,  both  of  which  are  worked  simultaneously  from  the  low-pres- 
sure engine  shown  at  the  lower  portion  of  the  figure.     Air  first  enters  the  cylinder  A  from  above, 

passes  to  the  condenser  D,  from  which  in  the  direction  of  the  arrow  it  passes  to  a  similar  receptacle 
E,  thence  down  as  indicated  by  dotted  lines  to  another  cooler  F.  Within  these  chambers  are 
arranged  series  of  pipes  through  which  the  blast  passes,  and  which  are  surrounded  by  a  current  of 
cold  water  that  enters  at  G  (dotted  lines,  Fig.  2365),  passes  up  through  the  cooler  F,  through  the 
pipe  H,  through  the  next  cooler,  and  emerges  at  /.  The  effect  of  this  water  is  to  abstract  a  portion 
of  the  heat  imparted  by  compression,  reducing  the  temperature  of  the  air  heated  by  compression  to 
a  few  degrees  above  that  of  its  natural  state,  the  extent  of  this  reduction  depending  upon  the  tem- 
perature of  the  water  and  the  length  of  time  the  air  is  submitted  to  its  action.  In  this  condition 
the  air  enters  the  cylinder  B,  where  the  expansion  takes  place  under  gradually  diminishing  pressure 
regulated  by  automatic  valves  worked  by  the  expansive  force  of  the  air  itself.  From  the  cylinder  B 
the  air  escapes  into  the  space  to  be  refrigerated.  The  refrigerator  used  consists  of  a  double-cased 
rectangular  wooden  chamber,  the  space  between  the  casings  being  filled  with  loose  cotton  or  other 
non-conductor  of  heat.  In  this,  through  apertures  in  the  cover,  metallic  cases  containing  the  water 
to  be  frozen  are  inserted  ;  and  to  insure  the  air  coming  in  contact  with  all  parts  of  these  cases,  zig- 
zag partitions  are  placed  in  the  compartments  between  them. 



Kirk's  apparatus  is  adapted  for  cooling  liquids  without  making  ice.  The  water  which  removes  the 
heat  caused  by  compression,  and  that  to  be  cooled,  are  injected  as  a  shower  through  the  compressed 
and  expanded  air  of  the  hot  and  cold  chambers,  and  are  withdrawn  by  simple  valves.  When  driven 
with  compound  engines,  a  surface-condenser  is  attached,  which  enables  clear  water  for  divers  purposes 
to  be  warmed  by  the  exhaust  steam.  In  Mignot's  machine  the  water  is  injected  in  the  form  of  spray 
into  the  very  midst  of  the  air  as  it  is  being  compressed  in  the  compressing  cylinder.  The  cold  air 
produced,  being  about  60°  below  the  freezing-point,  is  conveyed  through  a  trough  with  large  cells 
containing  the  water  to  be  congealed,  and  escapes  at  about  4°  above  the  freezing-point.  The  inject- 
ing of  the  spray  diminishes  the  work  to  be  done  in  compressing  the  air.  In  Gorrie's  apparatus  water 
is  injected  on  that  side  of  the  compressing-piston  at  which  condensation  is  taking  place.  The  con- 
densed air  passes  through  a  worm  surrounded  by  cold  water  to  a  reservoir,  whence  it  is  admitted  to 
an  auxiliary  pump  driven  by  the  expansion  of  the  compressed  air  in  which  it  is  expanded,  cooling  a 
non-congealable  fluid  in  a  jacket  surrounding  the  pump-cylinder.  This  abstracts  the  heat  from  the 
water  contained  in  a  reservoir  in  a  chamber  above  the  pump,  causing  its  congelation. 

Fig.  2366  represents  M.  E.  Carre's  apparatus  for  freezing  water  in  caraffes  for  table  use.  It  con- 
sists of  a  comparatively  large  air-pump  A,  but  not 
too  large  for  being  worked  by  one  man;  the  lever 
attached  to  the  handle  is  much  longer  than  is  rep- 
resented here.  The  horizontal  cylinder  B  below 
contains  sulphuric  acid,  or  some  other  hygroscopic 
substance  (for  instance,  solid  chloride  of  calcium), 
which  will  absorb  watery  vapor.  The  bottles  in 
which  the  water  is  frozen  are  made  of  heavy  glass, 
strong  enough  not  to  collapse  by  atmospheric  pres- 
sure when  the  vacuum  is  made  inside.  They  are  at- 
tached  by  an  air-tight  India-rubber  collar  or  ring  to 
a  tube  connected  with  the  vessel  containing  the  sul- 
phuric acid  or  its  equivalent,  while  another  part  of 
this  vessel  is  connected  by  means  of  a  bent  tube 
with  the  bottom  of  the  air-pump.  It  is  seen  that 
the  raporfi  arising  from  the  water  must  first  pass 
over  the  sulphuric  acid  in  the  lower  horizontal  cyl- 
inder before  arriving  at  the  air-pump,  to  be  ex- 
pelled by  the  latter.  The  bottles  are  filled  with 
cold  water,  as  seen  at  the  left,  and,  being  attached 
to  the  machine  as  shown,  and  the  pump  worked 
rapidly  and  with  strokes  of  the  fullest  possible 
length,  it  is  found  that  after  the  water  has  boiled 
from  the  beginning  of  the  operation,  after  50  or  60  strokes,  or  a  time  of  scarcely  one  minute,  about 
one-fourth  of  it  will  have  evaporated,  and  the  remaining  three-fourths  will  suddenly  freeze. 

Etuer  Machines.— Under  this  heading  may  be  classed  all  those  machines  in  which  the  cold  is  pro- 
duced by  the  evaporation  of  a  volatile  liquid,  to  effect  which  there  is  no  direct  application  of  heat. 
They  therefore  include  the  apparatus  which  employs  methylic  or  sulphuric  ether,  gasoline,  chymo- 
gene,  and  other  derivatives  of  petroleum,  methylic  oxide,  and  trimethyline.  The  tension  of  ether 
vapor  is  weak.  At  27°  of  cold  it  is  but  a  trifle  above  a  vacuum,  2  or  3  lbs.,  and  hence  the  evapora- 
tion is  carried  on  in  vacuo  by  the  aid  of  pumps  of  large  capacity.  The  obstacles  encountered  are  the 
tendency  of  the  ether  to  acidify,  the  danger  of  conflagration  of  the  inflammable  vapor,  and  the  diffi- 
cultv  of  preventing  entrance  of  air  to  the  working  cylinder.  The  ether  may  be  re-used  if  the  stuff- 
ing-boxes are  kept  in  perfect  order.  A  large  number  of  machines  of  this  class  are  in  use,  in  many 
of  which  the  difficulties  above  noted  are  greatly  reduced.  One  of  the  best  examples  is  Messrs.  S'«l- 
delcy  and  Mackayh  machine,  where  the  working  fluid  is  sulphuric  ether.  This  is  vaporized  in  a 
partial  vacuum  and  absorbs  heat  from  brine  during  its  vaporization.  The  vapor  thus  produced  is 
subsequently  compressed  and  delivered  into  a  condenser,  where  it  is  liquefied,  to  be  again  subsequently 
vaporized,  and  so  on  through  a  continuous  cycle  of  operations.  The  power  which  is  used  to  produce 
the  circulation  of  the  ether  and  the  brine  through  the  apparatus  is  derived  from  a  Galloway  boiler 
6  ft.  6  in.  in  diameter  by  22  ft.  long.  The  steam  is  supplied  at  55  lbs.  pressure  to  a  pair  of  hori- 
zontal compound  engines,  having  respectively  a  high-pressure  cylinder  of  18  in.  diameter  and  a  low- 
pressure  cylinder  of  28  in.  diameter,  the  stroke  in  both  cases  being  3  ft.  3  in.  The  engine  air-pump 
is  driven  off  the  crank-shaft  by  means  of  a  small  vibrating  beam  at  the  end  of  the  high-pressure 
engine  bed,  and  is  vertical.  The  ether  vacuum-pumps  are  horizontal,  and  worked  direct  from  the 
piston-rods  of  the  steam-cylinders ;  they  are  of  34  in.  diameter  by  3  ft.  3  in.  stroke.  Two  water- 
circulating  pumps  are  provided  for  the  pumping  of  the  brine  and  the  fresh  water  through  the  various 
portions  of  the  establishment,  and  are  driven  by  the  same  pair  of  engines,  as  shown  in  Fig.  2367. 
A  is  the  high-pressure  cylinder,  B  the  low-pressure  cylinder,  C  C  the  two  ether-vacuum  pumps,  D  D 
the  water-circulating  pumps,  E  the  feed-pump  for  boiler,  i^the  engine  air-pump,  G  the  engine  con- 
denser, h  h  the  governors,  and  I  and  k  pipes  connecting  the  vacuum-pumps  with  the  ether-condensers. 
In  dealing  with  the  cycle  of  operations  of  which  we  have  sketched  the  outline  above,  we  will  com- 
mence with  the  liquid  ether  as  it  is  in  contact  with  the  brine-cooling  surfaces  from  which  it  has  to 
absorb  heat.  The  brine-cooling  apparatus  is  a  vessel  like  an  ordinary  surface-condenser  traversed 
by  tubes,  which  are  charged  with  strong  brine.  The  ether  which  is  in  contact  with  the  exterior  of 
the  tubes  is  here  vaporized  under  a  vacuum  of  about  23i  in.  of  mercury,  and  at  a  temperature  of  21°, 
the  vapor  being  drawn  off  by  the  ether-pump,  which  then  compresses  and  delivers  it  to  the  ether- 
condenser  at  a  pressure  of  about  3  lbs.  per  square  inch  and  temperature  of  110°.     The  ether  vapor, 



however,  does  not  pass  direct  from  the  brine-refrigerator  into  the  ether-pump,  but  is  on  its  way  to 
the  latter  first  caused  to  pass  through  a  tubular  vessel  in  which  is  contained  the  liquefied  ether  on 
its  return  journey  for  re-use.  The  vaporized  ether  here  absorbs  some  of  the  heat  contained  in  this 
returning  liquid  ether,  and  becomes  somewhat  warmer  in  consequence,  and  passing  onward  it  finally 

flows  into  the  vacuum-pump,  not  at  21°  as  it  left  the  brine,  but  warmed  to  45°.  The  compression  it 
receives  by  the  vacuum-piston  as  it  is  driven  out  of  the  pump  raises  the  temperature  to  110°,  as 
already  mentioned.  The  ether  vapor,  discharged  from  the  pump  at  3  lbs.  pressure  and  110°  tempera- 
ture, passes  through  a  surface-condenser  formed  of  small  horizontal  copper  tubes  fixed  into  metal 
tube-plate  chambers  at  each  end,  round  about  which  tubes  is  a  constant  stream  of  water,  flowing  in 
at  the  bottom  and  out  at  the  top  of  the  chamber.  This  water  enters  at  the  natural  temperature  of 
the  supply,  62°,  and  passes  off  warmed  to  74°  by  heat  absorbed  from  the  ether  vapor  within  the  tubes. 
The  warmed  water  is  pumped  up  to  a  tank  elevated  to  the  highest  part  of  the  building,  from  whence 
it  is  allowed  to  descend  in  contact  with  the  surrounding  atmosphere,  by  which  means  it  becomes 
cooled  ready  for  re-use.  Returning  for  a  while  to  the  ether,  which  is  sent  back  to  the  first  vessel  or 
brine-refrigerator,  it  must  be  explained  that  another  important  apparatus  intervenes  between  the 
inflowing  supply  of  liquid  ether,  which  is  at  a  pressure  of  3  lbs.  per  square  inch,  and  the  refrigerator 
from  which  it  is  to  pass  under  the  vacuum  of  23  in.  to  the  pump.  This  is  the  governor,  consisting 
of  a  small  vessel  containing  an  inverted  valve  attached  to  a  lever  and  balance-weight,  and  a  ball- 
float.  The  adjustments  of  this  governor  are  such  that,  as  the  vessel  becomes  filled  with  the  return- 
ing supply  of  ether,  the  valve  becomes  depressed  by  the  weight  of  the  supply,  and  some  portion  of 
the  fluid  is  permitted  to  pass  away  to  the  refrigerator,  but  only  so  much  as  allows  the  valve  again  to 
close,  and  maintain  the  relative  differences  of  pressure  unimpaired.  We  must  now  follow  the 
course  of  the  brine,  cooled  to  a  temperature  of  21°,  which  has  been  prepared  as  we  have  described, 
and  which,  having  been  thus  cooled,  is  ready  for  the  purpose  for  which  it  has  been  formed,  viz.,  the 
production  of  pure  and  clear  ice  for  commerce.  The  water  to  be  frozen  passes  into  a  series  of  tanks 
formed  of  wrought-  and  cast-iron  water-spaces  or  walls,  about  3  in.  thick  and  about  4  ft.  deep, 
placed  vertically,  and  connected  at  the  ends  and  in  the  centre  of  their  length  in  such  a  manner  as  to 
form  a  number  of  cells  about  3  ft.  6  in.  long,  4  ft.  deep,  and  12  in.  wide,  the  bottom  being  some- 
what narrower  than  the  top  to  facilitate  the  removal  of  the  slab  of  ice  when  frozen.  There  are 
three  rows  of  these  tanks,  each  row  being  subdivided  into  six  main  divisions  containing  twenty-four 
cells.     When  it  is  desired  that  the  process  of  freezing  shall  begin,  the  cold  brine  is  caused  to  pass 



first  of  all  through  the  walls  of  a  tank  containing  cells  of  cold  water.  These  cells  of  water  in  due 
course  become  frozen  throughout  by  the  continual  flow  of  cold  brine  at  an  initial  temperature  of  21° 
through  the  3-in.  water-space  walls.  In  regular  and  constant  work,  however,  the  arrangement  differs 
somewhat,  for  it  is  desirable  that  the  currents  of  cooling  fluid  and  of  water  to  be  cooled  shall  circu- 
late in  opposite  directions.  Therefore  in  practice  the  brine  of  21°  temperature  is  passed  through  a 
tank  of  ice  that  is  approaching  its  completion  in  the  process  of  freezing,  and  then  having  been 
warmed  by  this  duty  to  say  24°,  it  is  passed  on  to  tank  No.  2,  whence  it  passes  on  to  tank  No.  3  at 
say  28°,  and  finally  out  from  No.  4  at  33°.  The  water  supplied  to  No.  4  thus  is  the  first  to  become 
congealed  in  regular  course,  and  forms  the  outer  shell  of  the  future  block.  After  a  period  of  say  1 2 
hours,  the  flow  of  brine  is  changed,  and  that  of  a  cooler  temperature,  viz.,  24°  (to  be  raised  to  28° 
by  its  duty),  is  made  to  flow  round  this  tank  in  place  of  that  which  had  been  circulating,  and  again  in 
another  12  hours  the  next  change  is  made,  and  brine  of  about  22°  (about  to  be  raised  to  24")  is 
made  to  flow  round  the  same  tank ;  and  a  final  flow  of  fresh  brine  from  the  refrigerator  at  the 
greatest  degree  of  cold  finishes  off  the  block  and  leaves  it  at  that  temperature  or  thereabouts.  Thus 
no  very  sudden  changes  of  temperature  are  brought  to  bear  upon  any  portion  of  the  structure,  and 
both  economy  of  result  and  duration  of  parts  are  insured.  The  consumption  of  fuel  keeps  at  about 
the  same  rate  as  at  the  time  of  trial,  viz.,  about  20  cwt.  of  coal  for  the  production  of  8  tons  of  ice. 
The  daily  (24  hours)  produce  is  from  22  to  23  tons.     (See  Engineering,  xxiii.,  599.) 

17ie  Sicbc  and  West  machine  consists  of  refrigerator,  condenser,  air-pump,  and  ice-making  box. 
When  the  air-pump  is  set  in  motion,  the  ether  in  the  cooling  vessel  evaporates,  and  of  course  absorbs 
heat  from  the  tubes  by  which  the  cooling  vessel  is  traversed.  The  ether  vapor  thus  produced  is 
forced  by  the  air-pump  into  the  condenser,  where,  under  the  combined  influence  of  the  pressure  and 
the  cooling  action  of  the  water  circulating  through  the  condenser,  it  resumes  the  liquid  form  and 
returns  through  a  small  tube  to  the  refrigerator,  where  it  is  again  changed  to  gas.  The  process  is 
continued  with  the  use  of  the  same  ether  as  long  as  the  machine  is  kept  working.  The  great  cold 
produced  in  the  cooling  vessel  acts  on  the  fresh  water  to  be  frozen  in  the  ice-box  by  means  of  a  cur- 
rent of  salt  water  introduced  into  the  tubes  which  pass  through.  The  temperature  of  the  salt  water 
decreases  quickly  on  its  way  through  the  refrigerator,  on  account  of  the  heat  being  absorbed  from 
it  by  the  ether  changing  into  gas,  and  it  then  circulates,  with  a  temperature  considerably  below  the 
freezing-point  in  the  ice-box,  round  a  number  of  iron  or  copper  vessels  rilled  with  fresh  water  to  be 
frozen  into  ice.  The  suit  wafer,  the  temperature  of  which  increases  again  by  coming  into  contact 
with  the  vessels  containing  the  fresh  water,  is  sent  back  to  the  refrigerator,  where  its  temperature  is 
again  reduced. 

In  Johnston  and  Whtielaw's  machine,  bisulphide  of  carbon  after  being  vaporized  is,  with  the  air 
forced  in  by  the  air-pump,  conducted  through  chambers  containing  oil,  which  absorbs  the  greater 
part  of  the  moisture  of  the  gas,  the  moisture  of  the  air  being  taken  up  by  chloride  of  calcium  in  a 
pipe  leading  to  the  air-pump.  In  Vander  1 1 5  ydt  \s  machine,  naphtha,  gasoline,  rhigolene,  or  chymo- 
gene  is  evaporated  by  an  air-pump  and  forced  through  a  freezer  in  which  are  vessels  containing 
water,  surrounded  by  inclosing  vessels  tilled  with  glycerine,  the  outside  being  surrounded  by 
cryogene.  The  evaporation  of  the  cryogene  causes  the  freezing  of  the  water.  Chymogene,  like 
ether,  has  a  very  weak  tension  at  a  comparatively  high  temperature,  the  point  of  ebullition  being  as 
high  as  40°  F.  It  requires  large  pump  capacity  and  a  high  vacuum,  and  it  is  open  to  the  objection 
of  inflammability.  The  same  difficulties  attend  the  use  of  methyline,  the  boiling  point  of  which 
varies  from  37.4°  to  53.6°  F.,  according  to  the  impurities  and  secondary  products  mixed  with  the 
material.     Most  metals  are  attacked  by  methyl-ammoniacal  products,  and  iron  must  be  exclusively 

used.     The  properties  of  methy- 
2368.  lie  oxide  are  analogous  to  those 

of  methylic  ether ;  that  is,  it 
gives  very  high  pressures  at  68° 
F.,  at  least  from  8  to  1 2  atmos- 

Holders  machine  is  adapted  to 
the  use  of  chymogene,  gasoline, 
or  other  easily  volatilized  liquid. 
Its  operation  will  be  understood 
from  Fig.  2368.  A  is  the  re- 
frigerator-cylinder, in  which  is  a 
coiled  pipe  through  which  a  non- 
congealable  liquid  s  circulates. 
Inside  the  cylinder  which  rotates 
is  the  volatile  liquid  a,  which  is 
evaporated  from  the  pipe-surface 
by  the  aid  of  the  pump  B,  which 
transmits  it  to  the  condenser  C, 
where  it  is  reliquefied  and  sent  back  to  the  cylinder  A.  The  non-congealable  liquid  goes  to  a  dis- 
tributing pan  I),  through  which  it  falls  in  fine  jets,  and  is  traversed  by  an  air-blast  I,  which  is  thus 
cooled.  The  circulation  of  the  air,  cold  liquid,  and  volatile  liquid  currents  will  readily  be  understood 
from  the  figure. 

The  Pictet  System. — The  principle  of  the  system  of  refrigerating  machinery  devised  by  M.  Raoul 
Pictet  is  the  volatilization  of  anhydrous  sulphurous  oxide,  a  colorless  liquid,  having  a  specific  gravity 
of  1.6,  and  remaining  fluid  under  a  pressure  of  from  2  to  3  atmospheres.  When  allowed  to  escape  in 
air  it  vaporizes  rapidly,  producing  a  decrease  of  temperature  of  135°  F. ;  and  if  a  teaspoonful  of  the 
liquid  be  poured  into  a  wine-glass  of  boiling  water,  the  latter  instantly  freezes  solid.     The  point  of 



ebullition  of  the  oxide  is  14°  F.,  under  the  atmospheric  pressure.  The  whole  apparatus  is  extremely 
simple,  as  is  indicated  by  the  annexed  diagram  of  a  small  machine,  Fig.  2369.  The  refrigerator  I> 
consists  of  a  tubular  copper  cylinder  placed  horizontally  in  a  tank  through  which  an  uncongealable 
liquid  (solution  of  glycerine,  chloride  of  magnesium,  or  various  salts)  is  circulated  by  means  of  a 


small  propeller-wheel.  The  moulds  or  cans  H,  for  making  the  ice,  may  either  be  placed  in  the 
refrigerator-tank,  or  in  a  separate  tank  specially  prepared.  The  sulphurous  oxide  is  volatilized  in  the 
refrigerator  D  by  a  pump  A,  which  sucks  the  oxide  from  the  refrigerator  through  the  tube  B  (pro- 
ducing intense  cold,  which  is  communicated  to  the  surrounding  liquid),  and  then  forces  the  vapor 
through  the  tube  C  into  the  condenser.  The  condenser  E  is  a  tubular  copper  cylinder  similar  to  the 
refrigerator ;  a  current  of  cold  water  is  kept  constantly  flowing  through  its  tubes,  which  abstracts 
the  heat  from  the  vapor  and  brings  it  back  to  a  liquid  form.  A  tube  returns  the  liquid  sulphurous 
oxide  to  the  refrigerator  to  be  revolatilized,  while  a  stop-cock  F  regulates  the  supply.  The  pump  A 
used  is  double-acting,  and  of  iron.  The  piston  is  of  metal,  without  packing.  Its  action  is  very  easy 
owing  to  the  lubricating  nature  of  the  oxide.  The  pump  may  be  driven  either  direct  by  an  engine 
or  by  a  belt  from  shafting. 

The  large  plants  for  making  ice  are  in  principle  the  same  as  the  small  one  described  above,  but  with 
certain  alterations  of  the  apparatus  on  account  of  the  size.  The  refrigerator,  a  plain  copper  tubular 
boiler,  is  immersed  horizontally  in  a  tank,  and  is  charged  with  1,760  lbs.  of  anhydrous  sulphurous 
oxide  once  for  all.  (The  oxide  comes  in  copper  bottles  containing  about  200  lbs.  each.)  Through 
this  tank  a  mixture  of  glycerine  and  water  is  made  to  circulate  by  means  of  a  rotary  pump.  The 
solution  of  chloride  of  magnesium  gives  equally  as  good  results  as  glycerine  and  water,  is  less  expen- 
sive, and  as  it  barely  freezes  at  — 25°  F.  (57°  below  the  freezing  of  water),  an  intense  cold  may  be 
obtained  for  special  purposes.  The  moulds  or  cans  of  galvanized  iron,  containing  the  water  to  be 
congealed,  are  placed  in  a  large  tank  communicating  with  the  small  tank  holding  the  refrigerator. 
The  sulphurous  oxide  is  vaporized  in  the  refrigerator,  and  the  vapors  generated  are  aspirated  by  a 
double-acting  aspiration  and  compression  pump.  This  pump  is  a  plain  cast-iron  cylinder,  fitted  with 
inlet  and  outlet  valves,  and  jacketed  with  a  circulation  of  water.  The  piston  is  hollow,  and  the  pis- 
ton-rod, which  is  also  hollow,  is  cooled  by  a  circulation  of  water.  The  cold  produced  by  the  volatiliz- 
ing of  the  oxide  in  the  refrigerant  is  transmitted  to  the  liquid  surrounding  and  passing  through  the 
tubes  of  the  latter.  This  liquid  flows  by  its  own  weight  into  the  large  tank,  communicating  its  cold 
to  the  water  in  the  cans,  which  freezes  to  ice. 

The  oxide  vapors,  entering  the  pump  from  the  refrigerator  at  a  vacuum  of  about  half  a  pound  to 
2  lbs.,  are  compressed  to  about  one-fifth  of  their  original  volume,  the  temperature  rising  to  nearly  200°. 
The  pressure  at  which  the  oxide  is  compressed  is  usually,  in  New  York,  2^-  atmospheres  (35  lbs.),  and 
in  the  hottest  climates  does  not  exceed  4+  atmospheres  (68  lbs.).  The  oxide  is  returned  under  pres- 
sure to  the  condenser,  placed  in  an  upright  iron  tank  to  the  rear  of  the  compression-pump.  The  cold 
water  freely  circulating  through  this  tank  cools  the  oxide  and  carries  away  the  heat.  The  liquid 
oxide  returns  to  the  refrigerator  by  two  long  narrow  pipes,  the  admission  being  regulated  by  stop- 
cocks, and  is  vaporized  anew.  The  operation  is  thus  perfectly  continuous.  Under  the  low  pressure 
employed  no  difficulty  as  to  leaks  occurs,  it  being  easy  to  keep  all  the  joints  tight.  No  air  can  enter 
the  oxide-pump,  the  pressure  of  the  oxide  as  it  enters  being  nearly  that  of  the  atmosphere  or  a  trifle 
below  it.  The  loss  of  oxide  does  not  exceed  half  a  pound  per  week.  The  solution  in  the  tank  very 
rarely  needs  renewal  or  additional  material,  and  is  always  cheap. 

Mr.  L.  F.  Beckwith,  engineer  of  the  Pictet  Ice  Company,  furnishes  the  following  data  as  to  the 



theoretical  and  practical  considerations  governing  the  working  of  the  machine :  "  The  heat  absorbed 
by  the  water  passing  through  the  condenser,  and  carried  off  by  this  water,  is  equal  to  the  latent  heat 
abandoned  by  the  sulphurous  oxide  in  passing  from  a  gaseous  to  a  liquid  state,  added  to  the  heat 
given  to  the  sulphurous  oxide  by  the  work  of  compression  of  the  pump.  The  latent  heat  absorbed  by 
the  oxide  from  the  freezing  mixture  has  been  obtained  by  the  latter  from  the  water  in  the  cans  dur- 
ing the  volatilizing  of  the  oxide  in  the  refrigerant.  The  heat  given  to  the  oxide  by  compression  is  the 
equivalent  of  the  work  produced  by  the  steam-engine,  less  that  absorbed  by  friction  and  the  run- 
ning of  the  other  parts  of  the  machinery.  As  an  example,  if  the  engine  indicates  76  lbs.,  we  have, 
deducting  power  required  to  run  air-pump,  condenser,  feed-pump,  circulating-pump,  hoisting-gear, 

33000  x  60  min.  x  57  lbs.       ,.„,_.       ..      ,  ,  ,  .     ,     . 

friction,  etc.  (25  per  cent.),  —  =5™  -  =  146,194  units  of  heat  per  hour,  equivalent 

to  the  work  produced  by  the  engine  in  compressing  the  oxide.  Now,  to  produce  ice  from  water  put 
into  the  cans  at  78°  R,  it  is  necessary  to  withdraw  from  each  pound  (46  +  142=)  188  units  of  heat; 
and  if  1,500  lbs.  are  made  per  hour,  the  amount  withdrawn  is  (1,500  x  188  =)  282,000  units  of  heat. 
The  water  of  condensation  passing  through  the  tubes  of  the  oxide-condensers  is  increased  in  temper- 
ature from  6°  to  7°  F. ;  about  1,100  lbs.  of  water  passes  through  per  minute;  therefore,  with  an 
average  of  6-T  F.,  (1,100  x  61  x  60  min.  =  )  429,000  units  of  heat  are  carried  off  per  hour.  This 
amount  approximates  closely  to  the  sum  of  the  heat  produced  by  the  work  of  compression  of  the 
engine  and  the  latent  heat  given  up  by  the  oxide  in  liquefying,  and  which  it  had  taken  from  the  water 
through  the  medium  of  the  cooling  mixture  of  glycerine  and  water,  viz.:  14t.,194  +  282,000  =  428,194 
units  of  heat.  The  amount  of  coal  used  per  pound  per  hour  is  2.6  lbs.  We  have  then,  for  coal  used 
in  work  of  compression  of  oxide  and  production  of  ice,  57  x  2.6,  or  148  lbs.  for  1,500  lbs.  of  ice,  or 
208  lbs.  for  2,000  lbs.  of  ice;  the  coal  at  $4  per  ton  amounts  to  41£  cents.  Commercially,  76  lbs. 
being  used  for  running  all  the  machinery,  we  have  2.6  lbs.  x  76  lbs.  =  204  lbs.  for  1,500  lbs.  of  ice, 
or  272  lbs.  for  2,000  lbs.  of  ice ;  the  coal  at  $4  per  ton  amounts  to  54  cents." 

Ammonia  Machines  differ  entirely  from  those  previously  described,  in  which  ether,  etc.,  is  used,  in 
that  no  pumps  are  used  or  other  direct  application  of  power  is  made  to  restore  the  gaseous  mate- 
rial  bo  B  liquid  form  by  production  of  pressure.  Either  a  saturated  solution  of  ammonia  or  the  lique- 
fied ammonia  is  used.  The  first  are  necessarily  worked  under  a  high  pressure,  in  hot  climates,  with 
the  thermometer  at  95°,  the  pressure  reaches  300  lbs.  per  square  inch,  and  it  i*  ni'ver  less  than 
from  180  to  225  lbs.  In  liquefied  ammonia  machines  the  pressure  is  from  135  to  180  ibs.  The  diffi- 
culties are  chiefly  the  frequent  ami  heavy  leaks,  the  corrosive  action  of  the  ammonia  on  metals,  the 
impossibility  of  using  grease  as  a  lubricant,  and  the  deposits  which  form  in  the  boilers. 

Vaas  and  Littmann's  machint  is  represented  in  Fig.  2370.  This  consists  of  the  boiler  A,  condenser 
B,  gas-holder  C,  ice-box  D,  absorption-cylinder  L\  temperature-exchanger  F,  cooler  O,  and  pump  H. 

The  boiler  A  is  first  half  filled  with  solution  of  ammonia,  which  is  caused  to  evaporate  by  the  applica- 
tion of  heat,  and  the  gas  thus  formed  is  forced  through  the  pipe  I  into  the  worm-pipe  of  the  conden- 
ser B,  and  thence  through  the  pipe  2  into  the  gas-holder  O.  From  the  gas-holder  the-gas  is  conducted 
by  the  pipe  3  to  the  valve  on  the  top  of  the  ice-box  I),  which  is  in  connection  with  the  worm-pipe  in- 
side the  ice-box.  The  gas  on  its  passage  through  the  worm-pipes  of  the  condenser  (which  are  always 
surrounded  by  cold  water)  is  condensed"  and  the  liquid  passes  through  the  valve  to  the  worm-pipes  in 



the  ice-box,  where  it  again  begins  to  evaporate,  taking  up  at  the  same  time  heat  from  the  solution  of 
chloride  of  calcium,  in  which  the  worm-pipes  in  the  ice-box  are  submerged.  This  absorption  of  heat 
so  lowers  the  temperature  of  the  solution  of  chloride  of  calcium  as  to  render  it  capable  of  turning  the 
fresh  water  contained  in  the  ice-cases  to  ice.  The  ammonia  which  has  been  volatilized  in  the  pipes  of 
the  ice-box  passes  through  the  pipes  4  to  the  absorption-cylinder  E,  and  at  the  same  time  the  weak 
solution  of  ammonia,  which  has  lost  the  gas  by  heat,  passes  out  of  the  boiler  by  the  pipe  5  into  the 
exchanger  F,  through  the  cooler  G,  into  the  absorption-cylinder  F,  where  it  absorbs  the  gas  which 
comes  from  the  ice-box ;  and  from  these  it  is  pumped  back  by  the  pump  7  into  the  boiler  to  be  again 
heated.  A  machine  of  this  kind  for  making  200  lbs.  of  ice  per  hour  is  stated  to  require  a  2-horse- 
power  engine  to  drive  it. 

Tlie  Atlas  machine,  Fig.  2371,  has  a  still  A,  lime-drier  B,  condenser  and  tank  C,  and  refrigerating 
tank  D.  The  still  incloses  a  coil  of  pipe,  which  is  covered  by  the  liquid  ammonia.  The  gas  arising 
passes  through  the  lime-drier,  which  is  simply  a  cast-iron  cylinder  containing  unslacked  lime,  and 



thence  goes  to  the  pumps  E,  whence  it  passes  to  the  condenser  contained  in  the  tank  C,  where  it  is 
liquefied  by  pressure.  The  ammonia  stored  in  the  condenser  is  conveyed  through  a  pipe  to  a  distribut- 
ing manifold,  inclosed  in  the  refrigerating  tank  D. 

In  Reeve's  machine,  a  generating  vessel  is  charged  with  a  solution  of  ammonia,  and  a  fire  is  lighted 
under  the  boiler,  which  expels  all  the  air.  A  strong  solution  of  ammonia  is  then  pumped  to  the  top 
of  an  analyzing  cylinder  above,  and  as  the  solution  descends  the  different  plates  there  it  is  in  a  great 
measure  separated  from  the  water  by  the  steam.  The  ammonia  next  goes  to  a  rectifier,  where  it  is 
cooled  by  a  stream  of  cold  water,  and  rendered  perfectly  free  from  watery  vapor.  It  then  passes  to 
a  liquef  actor,  where  it  is  liquefied  by  the  mere  pressure  of  the  gas  itself ;  it  next  proceeds  to  a  cooling- 
cylinder,  and  then  to  a  second  cylinder,  where  it  resumes  the  gaseous  state,  cooling  the  liquid  inclosed 
in  the  coil.  The  now  exhausted  ammonia  passes  to  an  absorbing  vessel,  where  it  meets  with  the 
exhausted  liquor  from  the  generator  and  is  dissolved.  The  solution  is  now  pumped  through  a  hori- 
zontal heater,  where  it  meets  with  the  liquor  proceeding  from  the  boiler  into  the  top  of  the  analyzing- 
cylinder,  where  the  same  series  of  operations  is  repeated. 

M.  Ferdinand  Carre's  ammonia  machine  is  represented  in  Fig.  2372.  A  is  a  boiler,  which  contains 
an  aqueous  solution  of  ammonia.  This  boiler  is  heated  by  steam  led  by  the  tube  C  into  the  coil  B, 
the  water  of  condensation  of  which  escapes  in  the  condenser  D.  The  solution  being  heated  by  the 
steam,  the  gas  passes  by  the  tube  K  into  the  liquefier  L  L.  This  consists  of  a  tank  containing  coils, 
around  which  circulates  a  continuous  current  of  cold  water,  which  descends  from  the  reservoir  Z  by 
the  tube  h.  The  liquefied  ammonia  passes  through  a  tube  which  is  itself  contained  in  the  sleeve  P, 
and  goes  to  the  cooler  M.  In  this  receptacle  the  ammonia  liquid,  which  is  contained  in  a  coil  P,  is 
again  gasefied.  The  water  to  be  frozen  is  placed  in  long  cylinders  R,  which  are  plunged  in  a  non- 
congealable  liquid,  a  solution  of  chloride  of  calcium.  The  cylinders  with  their  frozen  contents  are 
removed  about  every  fifteen  minutes.     The  ammoniacal  gas,  disengaged  from  the  liquid  as  it  passes 



through  the  cooler-coil,  passes  through  the  tube  S  to  the  absorption-chamber  T,  following  the  tube  c. 
In  this  chamber  is  a  coil  surrounded  by  cold  water,  and  in  the  coil  the  gas  resumes  a  liquid  condition. 
The  liquid  is  then  pumped  back  into  the  boiler  A. 

From  experiments  made  by  Dr.  R.  Schmidt  of  Berlin  in  1870,  on  both  the  Carr6  ammonia  and  the 
Windhausen  compressed-air  machines,  the  following  results  were  obtained :  Experiments  were  made 
during  150  days,  12  hours  being  estimated  to  the  day ;  and  for  each  horse-power  96  lbs.  of  coal  were 
taken.  There  were  also  consumed  110  lbs.  of  sal-ammoniac  and  110  lbs.  of  chloride  of  calcium.  The 
results  were,  that  a  Carre  machine  produced  hourly  400  lbs.  of  ice  at  1£  cent  per  pound ;  the  running 


expenses  of  the  Windhausen  machine  were  one-third  higher,  and  the  cost  of  the  ice  nearly  2  cents  a 

From  tests  made  as  to  the  economy  of  producing  cold  dry  air  by  artificial  refrigeration,  instead  of 
the  damp  air  obtained  by  melting  ice,  in  which  a  Carre  apparatus  capable  of  producing  5  lbs.  of  ice 
per  minute  was  used,  the  following  result  among  others  was  reached :  It  was  found  that  300  lbs.  of 
natural  ice  were  required  to  reduce  the  temperature  of  a  room  from  80°  to  46°  F.  in  2  hours  and  20 
minutes,  which  effect  was  obtained  by  Carre's  apparatus  in  7  minutes  with  the  same  quantity  of  cold 
required  to  form  35  lbs.  of  ice ;  thereby  showing  that  8  times  as  much  ice  was  consumed  to  produce 
the  same  quantity  of  cold  air  as  was  supplied  by  the  apparatus. 



Machines  based  on  the  Use  of  Freezing  Mixtures. — Freezing  mixtures  are  combinations  of 
chemicals  which  in  dissolving  in  water  absorb  large  quantities  of  heat,  and  so  cause  notable  diminu- 
tions of  temperature.  The  following  are  well-known  mixtures  :  1.  Salt  1  part,  cracked  ice  1  part; 
temperature  obtained,  from  50°  to  10.4°  F.  2.  Water  10  parts,  muriate  of  ammonia  5  parts,  salt- 
petre 7  parts;  temperature  obtained,  from  50°  to  3.4°  F.  3.  Water  1  part,  muriate  of  ammonia  1 
part ;  temperature  obtained,  from  50°  to  14°  F.  4.  Sulphate  of  soda  8  parts,  hydrochloric  acid  5 
parts;  temperature  obtained,  from  64.4°  to  1.4°  F.  The  use  of  acids  is  always  disagreeable  and 
dangerous,  and  hence  it  is  preferable  to  employ  nitrate  or  hydrochlorate  of  ammonia. 

Proportions  of  various  Chemicals  to  be  added  to  four  parts  of  Water  to  produce  Temperatures  noted. 

Lowering  of 
Temperature,  in  De- 
grees Centigrade. 

4  parts  nitrate  of  ammonia 20" 

1  part         "                "         14.1 

5  parts  nitrate  of  ammonia  and  5  of  saltpetre,  22.0 

1  part  nitrate  of  ammonia 15.2 

1    "     sulphate  of  potash 2.9 

Lowering  of 
Temperature,  in  De- 
grees Centigrade. 

1  part  chloride  of  potassium 11.8 

1    "     sulphate  of  soda 8.0 

1    "     chloride  of  sodium 2.1 

1    "     nitrate  of  soda 9.4 

1    "     acetate  of  soda 10.6 

If,  instead  of  water  at  normal  temperature,  ice  or  snow  is  employed,  still  further  abstraction  of 
heat  is  secured.  The  greatest  attainable  lowering  of  temperature  by  the  aid  of  a  saline  mixture  is 
the  degree  at  which  the  solution  itself  congeals  This  is  shown  in  the  following  table,  the  chemi- 
cals noted  being  mixed  with  100  parts  of  snow: 

obtained,  in  De- 
grees Centigrade. 

10  parts  sulphate  of  potash —   1.9° 

20     "     carbonate  of  soda —  2.0 

13     "     nitrate  of  potash —  3.85 

30     "     chloride  of  potassium —10.9 

obtained,  in  De- 
grees Centigrade. 

25  parts  hydrochlorate  of  ammonia —15.4 

45      "     nitrate  of  ammonia —16.75 

50     "     nitrate  of  soda — 1*7.75 

33      "     chloride  of  sodium —21.3 

Sulphuric  acid  diluted  with  water  and  mixed  with  ice  gives  very  intense  cold.  Mingled  with  25 
per  cent,  of  its  weight  of  water  and  33  per  cent,  of  its  weight  of  ice  or  snow,  it  produces  a  refrigera- 
tion of  —32°  C,  and  with  equal  parts  of  acid  and  snow  of  —44°  C. 

A  simple  device  for  producing  ice  in  small  quantities  by  means  of  freezing-powders  has  been  in- 
vented by  M.  Toselli  of  Paris,  and  is  illustrated  in  Figs.  2373,  2374,  and  2375.     It  consists  of  a  cylin- 



drical  case  A,  Fig.  2373,  suspended  on  trunnions  in  a  frame,  and  capable  of  rotation  by  the  crank- 
handle  shown.  The  cylinder  is  open  at  both  its  extremities,  to  which  however  covers  are  fitted.  B, 
Fig.  2374,  is  a  nest  of  cylinders,  seven  in  number,  and  secured  between  heads ;  no  two  of  these  ves- 
sels are  of  the  same  size,  the  diameters  decreasing  from  the  largest  down,  in  regular  proportion. 
This  assemblage  of  cylinders  fits  into  the  case  A,  and  in  said  vessels  is  placed  the  water  to  be  con- 
gealed.    As  the  object  is  ultimately  to  produce  a  uniform  lining  of  ice  in  each  cylinder,  it  follows 



that  the  quantity  of  water  introduced  in  each  must  be  measured  with  accuracy.  This  is  easily  done 
by  the  tray  C,  in  which  there  is  a  ledge,  upon  which  the  nest  B  rests,  and  is  maintained  at  such  an 
angle  that  only  a  certain  amount  of  water  can  be  poured  out  of  the  cylinders,  which  amount  is  ob- 
viously directly  proportional  to  the  diameter  of  each  tube,  and,  all  being  parallel,  to  the  angle  of 
inclination.  The  compartments  are  next  inserted  in  the  case  A,  and  the  cover  replaced  and  secured. 
The  case  is  then  reversed  and  the  other  cover  taken  off,  so  that  a  mixture  of  equal  weights  of  nitrate 
of  ammonia  and  water  can  be  poured  in,  so  as  to  fill  the  interstices  of  the  tubes ;  this  done,  the  cover 
is  put  back  and  fastened,  and  the  apparatus  rotated  for  five  minutes  by  the  crank.  This  period 
suffices  to  produce  a  moderately  thick  film  of  ice  around  the  interior  of  each  cylinder,  and  these  films 
can  be  easily  taken  out ;  it  remains  only  to  fit  one  cylinder  of  ice  into  the  other,  and  so  to  continue 
until  all  are  fitted  together,  as  shown  in  Fig.  2375,  to  produce  a  solid  block  of  ice  weighing  11  lbs. 

The  same  inventor  has  also  contrived  a  dynamic  refrigerator,  which  consists  of  a  revolving  disk, 
formed  of  a  metallic  tube  bent  into  a  complete  spiral,  having  one  end  open  and  the  other  end  com- 
municating by  a  hollow  shaft  with  an  external  tube  communicating  with  a  worm  contained  in  a  sep- 
arate vessel,  and  terminating  in  a  discharge-pipe,  with  outlet  into  another  vessel  containing  the 
revolving  disk,  to  which  a  slow  movement  of  revolution  is  imparted  by  a  driving-pulley  and  belt, 
making  say  one  turn  per  second.  The  disk  is  half  immersed  in  cold  water,  and  as  the  exterior  sur- 
face of  the  disk  above  water  is  continually  wet,  it  exposes  considerable  evaporating  surface.  At  the 
same  time  a  continuous  stream  of  water  is  forced  through  the  hollow  spiral,  parting  with  some  of  its 
heat  under  the  influence  of  the  external  evaporation  and  radiation,  which  is  intensified  by  the  addi- 
tion of  a  ventilator.  The  current,  being  thus  lowered  in  temperature,  refrigerates  in  its  turn  the 
liquid  to  be  cooled  in  the  vessel.  The  lowering  of  temperature  thus  obtained  varies  according  to  the 
liytrrometric  condition  of  the  atmosphere;  the  minimum  effect  obtained,  under  the  most  favorable 
circumstances,  amounts  only  to  a  difference  of  5°  to  6C  F.,  while  the  maximum  difference  obtained 
in  sunlight  is  between  32°  and  33°  F. 

ICE-YACHT.  The  construction  of  this  form  of  vessel,  which  is  designed  for  traveling  upon  the 
frozen  surface  of  rivers,  etc.,  is  fully  detailed  below.  The  rigging  is  similar  to  that  of  ordinary  sail- 
ing sloops.     The  notable  feature  of  the  ice-yacht's  performance  is  its  great  speed,  which  often  ex- 

ceeds 65  miles  an  hour,  outstripping  (paradoxical  as  it  may  seem)  the  wind  which  impels  it,  except 
when  the  breeze  is  directly  astern. 

The  following  description  refers  to  the  Whiff,  which  was  exhibited  at  the  Centennial  Exposition 
by  her  owner,  Mr.  Irving  Grinnell : 

The  Whiff,  of  which  full  detailed  drawings  are  given  in  Figs.  2376  to  2379,  is,  as  will  be  seen, 
sloop-rigged.  The  hull,  if  it  may  be  so  called,  is  composed  of  the  keel  or  centre  timber  and  two 
curved  side  timbers,  joined  at  the  mast  by  two  curved  timbers  bolted  on  to  them,  and  at  the  stern 
by  a  semicircular  continuation.  The  mast  rises  from  the  keel  and  the  mast-bench,  the  chief  timber 
of  the  latter  being  the  runner-plank,  at  the  ends  of  which  two  runners  are  bolted.  This  runner- 
plank  is  bolted  to  the  under  side  of  the  side  bars,  and  runs  under  the  keel.  The  hull  proper  of  the 
boat  commences  at  the  mast-bench,  extending  over  less  than  half  its  width,  and  runs  back  in  the  form 
of  an  ordinary  boat  to  the  rudder  end.     The  keel  extends  from  here  to  a  little  way  beyond  the  mast, 



where  the  bowsprit  is  strapped  on  to  it,  and  extending  out  forms  the  only  hull  timber  in  front  of  the 
mast.  The  deck  occupies  the  hinder  part  and  less  than  half  of  the  hull.  The  rudder  consists  of 
a  movable  skate  or  runner,  worked  as  in  an  ordinary  vessel.  The  mast  and  bowsprit  are  very  rigidly 
stayed  by  wire-rope  shrouds.  From  the  general  design  down  to  every  detail,  the  object  has  been 
to  give  great  strength  and  rigidity  with  the  least  possible  amount  of  timbering  necessary  to  secure 
this  end. 

The  general  dimensions  of  the  Whiff  are  as  follows :  Total  length,  from  the  tip  of  her  bowsprit 
to  the  end  of  the  main  boom,  40  ft.  Total  height,  from  masthead  to  the  plane  of  the  runner  edges, 
25  ft.  3  in.  From  end  of  bowsprit  to  ex- 
tremity of  deck,  31  ft.  4  in.  The  mast  rises 
21  ft.  4  in.  from  the  deck  level,  and  has  a 
topmast  which  extends  3  ft.  8  in.  farther 
up ;  it  is  4  in.  in  diameter  at  the  bottom, 
and  3  in.  at  the  top.  The  bowsprit  is  15 
ft.  in  length,  3  in.  deep  at  the  ends,  curv- 
ing to  6  in.  where  it  is  strapped  by  an  iron 
band  on  to  the  keel.  It  is  additionally  se- 
cured to  the  keel  by  a  bolt  running  through 
both.  The  jibsprit  is  13  ft.  long,  2  in.  at 
ends,  rising  to  2-j  in.  in  diameter  at  the  cen- 
tre. The  main  boom  is  24  ft.  in  length,  is 
fastened  to  the  mast  by  an  eye  and  staple, 
and  is  2|  in.  at  the  ends,  rising  to  41.  The 
gaff  is  9  ft.  long,  2  in.  in  diameter,  and  is 
jawed  on  to  the  mast.  Runner-plank,  16 
ft.  long,  1  ft.  wide.  Runners,  4  ft.  10  in. 
long.  Rudder-skate,  2  ft.  5  in.  The  deck 
is  of  narrow,  closely  jointed,  alternate  slips 
of  cedar  and  spruce,  laid  across  the  boat, 
and  5J  in.  below  the  top  of  the  side 
bars.  The  mainsail  has  a  hoist  of  13  ft. 
8  in. ;  foot,  23  ft. ;  head,  8  ft.  4  in. ;  and 
leach,  24  ft.  3  in.  The  jib  has  a  hoist  of 
14  ft.  8  in.;  foot,  12  ft.  7  in.;  and  leach, 
19  ft.  10  in.  The  total  sail  area  is  347  sq. 
ft.  The  sails  are  made  of  heavier  canvas 
than  that  usually  used  for  a  sea-going  yacht 
of  the  same  size,  and  each  strip  is  double- 
bighted  to  give  the  sail  the  necessary  stiff- 
ness. The  mast,  bowsprit,  jibsprit,  keel, 
side  bars,  and  runner-plank  are  of  white 
pine.  The  boom  and  gaff  are  of  spruce. 
The  curved  timbers  which  brace  the  side 
bars  are  of  ash.  The  handrail  is  of  wal- 
nut, and  the  side  bars  are  cased  with  the 
same  wood,  being  also  ornamented  with  a 
gilt  beading. 

The  shoes  of  the  runners  are  cast,  and 
are  bolted  on  to  the  skates,  which  are  of 
white  oak,  by  means  of  four  screw-bolts 
each.  This  runner,  4  ft.  10  in.  long,  as  be- 
fore mentioned,  and  7  in.  high,  is  bolted 
between  two  horizontal  oaken  bars,  1  ft.  7 
in.  long,  41  ft.  deep,  and  2J  in.  wide,  which, 
in  their  turn,  are  bolted  to  the  runner-plank, 
the  whole  being  braced  to  the  runner-plank 
by  two  side  pieces.  The  bowsprit  is  strapped 
and  bolted  on  to  the  keel  as  shown  in  ele- 
vation and  section  in  Fig.  2378.  The  iron 
strap  is  2  in.  wide  and  half  an  inch  thick. 
The  jibsprit  is  fastened  to  the  bowsprit  by 
means  of  an  eye  and  staple.  The  shrouds 
are  kept  taut  by  means  of  turn-buckles,  like 
that  shown  in  Fig.  2378,  which  connect  them 
with  their  staples.  The  shrouds  are  of  the  best  galvanized  charcoal  iron,  seven-sixteenths  of  an  inch 
in  diameter.  A  black-walnut  handrail  runs  on  the  keel  from  the  mast  to  the  tiller.  As  the  rudder 
and  post  are  most  important  parts  of  the  yacht's  build,  we  have  given  the  full  details  in  Fig.  2379. 
The  shoe  is  bolted  on  to  the  oakon  rudder-skate,  2  ft.  5  in.  long,  by  three  screw-bolts,  the  latter 
being  pinned  on  to  the  rudder-post.  A  rubber  spring  on  the  rudder-post  is  set  between  the  shoulder 
and  the  cast-iron  bottom  plate  let  into  the  deck.  A  brass  top  plate  is  let  into  the  keel,  the  tiller 
being  fastened  to  the  rudder-post  by  a  screw-nut.  The  rudder-post  is  1  ft.  3£  in.  long.  The  tiller, 
whose  handle  is  bound  around  with  small  rope,  is  2  ft.  6  in.  in  length. 

The  rudder-shoes,  as  well  as  those  of  the  two  runners,  are  of  cast  iron.     Steel  has  been  tried,  but 







^uhut:  ?tcu^' 


[_.  e         lit. 



^ MUX.       ,  '    ,     **. 





was  found  to  be  too  hard.  If  the  ice  be  smooth,  and  free  from  snow,  etc.,  the  greater  speed  is 
obtained  with  sharp  skates ;  they  are  filed  so  sharp  that  they  cause  a  hand-nail  to  fluff  when  it  is 
drawn  over  them.  On  the  contrary,  when  there  is  snow-ice,  ice  with  a  rough  surface  or  partially 
covered  with  snow,  or  when  the  weather  is  moderate  and  disposed  to  thaw,  the  yacht  sails  much 
faster  with  slightly  dulled  shoes.  The  shoes,  sharpened  up  with  a  file,  can,  when  desired,  be  quickly 
roughened  with  emery-paper.  If  the  edges  need  sharpening,  a  fine  tile  or  an  oil-stone  will  accom- 
plish in  a  short  time  the  desired  result.  Steel  shoes  would  not  allow  of  these  sudden  transitions, 
while  those  of  cast-iron  do.  All  the  iron  work  on  the  Whiff  is  nickel-plated,  and  a  high  degree  of 
finish  is  observable  on  every  part  of  the  vessel. 

When  sailing,  a  sail-shelter  from  the  wind  is  erected  at  the  fore  part  of  the  deck,  if  desired. 

The  Whiff  is  ornamented  with  a  very  artistic  figurehead,  representing  a  griffin.  Being  built  of 
the  best  possible  material,  and  elaborately  gotten  up,  this  ice-yacht  cost  her  owner  $700  ;  but  a  boat 
equally  good,  without  the  same  degree  of  finish,  can  be  built  for  from  $350  to  $400.  (See  Scientific 
American  Supplement,  No.  63.) 

IMPACT.     See  Dynamics. 

IMPETUS.     See  Dynamics. 

INCLINED  PLANE.  For  discussion  of  the  inclined  plane  as  one  of  the  mechanical  powers,  see 

Inclined  Planes  on  Railways. — The  heights,  lengths,  and  other  particulars  of  the  Gordon  and  Ma- 
hanoy inclined  planes  on  the  Philadelphia  and  Reading  Railway  are  as  follows : 

Dimensions,  etc.,  of  Inclined  Planes  on  Philadelphia  and  Reading  Railway. 





t  U 

a  | 
1  § 




+*      > 






*  H 
■3  2 

3  g 




Made  of 





Made  of 


1.  Gordon  ..    . 

2.  Gordon. ,    . . 
Mahanoy . . . 























Iron  wire. 
Steel  wire. 







Iron  wire. 


The  planes  are  described  as  follows  in  the  Engineer,  Feb.  2,  1877: 

"  The  track  down  the  Gordon  planes  is  double,  a  train  of  loaded  cars  ascending  on  one  track  and  the 
empty  cars  descending  on  the  other,  and  alternating  each  trip.  Lying  between  each  pair  of  ordinary 
rails  of  4  ft.  8-£  in.  gauge  are  others  of  3  ft.  4  in.  gauge,  extending  from  a  few  feet  at  the  head  of 
each  plane  respectively  down  the  incline,  and  each  terminating  in  a  small  tunnel  between  and  below 
the  ordinary  rails — to  receive  the  '  safety-trucks '  running  on  these  internal  rails — some  few  feet 
beyond  the  foot  of  the  plane.  The  internal  pairs  of  rails  are  spiked  to  the  same  sleepers  as  the  ordi- 
nary ones,  till  just  as  they  reach  the  tunnels  mentioned,  when  they  descend  by  a  rapid  incline,  and  lie 
out  of  sight,  allowing  the  cars  to  pass  clear  over  them.  The  safety-trucks,  or  '  Barneys,'  as  the  work- 
men term  them,  are  strongly  built  of  timber,  and  mounted  on  four  wheels  26  in.  in  diameter ;  the 

front  end  forms  a  spring  buffer  by  means  of  India-rubber,  or,  as  they  term  them  here,  'gum'  springs 
The  construction  will  be  readily  understood  from  Fig.  2380,  which  is  a  sectional  view.  The  oae  end 
of  main  rope  passes  down  under  the  front  of  truck,  to  keep  it  low  to  miss  the  axles  and  under-gear 
of  the  cars,  and  is  coiled  over  a  small  drum  on  the  truck  and  firmly  secured ;  the  rope  then  extends 


up  the  track,  passing  round  the  two  main  drums  in  a  manner  to  be  presently  described,  and  is  then, 
by  means  of  a  large  horizontal  sheave,  diverted  and  thrown  into  the  centre  of  the  other  track  and 
secured  in  the  same  manner  to  the  other  safety -trucks.  The  length  of  this  rope  is  so  adjusted  that 
the  one  safety-truck  is  standing  at  the  head  of  the  plane  while  the  other  is  out  of  sight  in  its  tunnel 
at  the  foot.  The  rear  ends  of  these  trucks  are  connected  together  by  a  tail  rope,  also  passing  round 
a  diverting  sheave  to  spread  the  rope  to  the  centre  of  tracks — thus  forming,  as  it  were,  an  endless 
rope  with  the  two  trucks  in  its  centre,  but  with  the  ropes  of  different  size.  The  main  one  is  2£  in. 
diameter  iron-wire  rope,  with  independent  iron-wire-rope  centre,  and  the  tail  rope  is  1£  in.  diameter, 
of  similar  make ;  its  puqjose  is  to  keep  the  main  rope  tight  and  the  trucks  equidistant,  and  prevent 
its  jerking  and  lashing  the  roadway,  and  it  also  insures  the  steady  ascent  and  descent  of  the  wagons. 
An  equal  tension  is  obtained,  and  the  variations  in  length  according  to  temperature  allowed  for,  by 
the  arrangement  of  the  movable  horizontal  rendering  sheave  around  whch  the  tail  rope  passes  at  the 
base  of  the  plane.  This  sheave  is  of  cast  iron,  8  ft.  diameter,  and  is  fixed  below  the  roadway,  and 
on  the  same  level,  and  a  little  in  the  rear  of  and  between  the  two  tunnels,  for  the  reception  of  the 
safety-trucks.  It  is  fixed  in  a  frame  with  small  wheels  running  on  a  pair  of  rails,  allowing  it  a  few 
feet  play  either  backward  or  forward  ;  to  the  back  of  this  carriage  carrying  the  sheave  is  attached  a 
chain  led  away  horizontally  by  a  system  of  pulleys  to  the  side  of  the  line ;  then  passing  up  to  the 
top  of  a  wooden  gallows,  it  is  fastened  to  a  suitably  weighted  box  sliding  vertically  up  and  down 
between  guides  as  the  carriage  moves  on  its  rails,  the  weight  of  the  box  of  course  being  adjusted  to 
keep  the  rope  at  the  right  degree  of  tension.  There  are  also  two  smaller  sheaves  or  pulleys  fixed, 
one  in  the  rear  of  each  tunnel,  spreading  the  tail  rope  out  as  it  leaves  the  larger  sheave  to  the  centres 
of  the  tracks.  The  small  pulleys  for  carrying  the  rope  are  made  of  wood,  and  fixed  at  intervals  of 
15  ft.  apart  centre  to  centre;  they  only  last  about  a  week  each.  The  life  of  a  main  rope  is  based 
on  its  tonnage  capacity,  and  it  is  limited  to  the  raising  of  2,000,000  tons;  after  having  performed 
that  amount  of  duty  it  is  removed  and  a  new  rope  substituted.  This  maximum  was  adopted  from  ex- 
perience, and  has  worked  very  well.  It  is  also  daily  subjected  to  a  rigid  examination,  and  should  a 
fibre  of  one  of  the  wire  strands  be  found  to  have  given  way,  the  rope  is  cut  to  ascertain  the  state  of 
the  interior,  it  being  often  found  worn  inside  from  the  abrasion  of  the  wires  on  each  other  when 
presenting  a  sound  exterior.  The  engine  and  boiler  houses  aic  situated  at  the  head  of  their  respec- 
tive planes.  There  are  15  boilers  to  each  pair  of  engines,  3  ft.  diameter  and  26  ft.  long,  plain 
cylindrical  type,  and  set  in  the  ordinary  way  with  a  flash  flue,  and  carry  a  pressure  of  75  lbs.  per 
square  inch.  This  kind  of  boiler,  aeldom  exceeding  3  ft.  in  diameter,  is  generally  used  throughout 
the  whole  of  the  mining  district. 

"The  machinery  is  situated  beneath  the  roadway,  and  consists  of  a  pair  of  engines  with  30-inch 
cylinders,  6  ft.  stroke,  with  link  motion,  and  coupled  on  the  edge  of  shaft,  on  which  is  fixed  one  of 
the  two  main  drums,  which  are  geared  together;  the  one  farthest  from  the  engine  is  fixed  a  little 
lower  than  its  fellow  to  allow  the  rope  to  clear  it ;  this  and  the  general  arrangement  will  be  under- 
stood by  reference  to  the  drawings.  Both  drums  are  the  same  size,  viz.,  12  ft.  54  in.  diameter;  the 
teeth  are  4|  in.  pitch  and  1(>-|  in.  on  face,  as  will  be  seen  by  the  section  of  rim  of  these  drums.  The 
centre  of  the  teeth  is  2  in.  to  one  side  of  the  centre  of  wheel,  while  the  centre  of  the  oak  blocks 
grooved  for  the  rope  is  8  in.  from  its  centre  on  the  opposite  side.  These  wood  blocks  are  inserted 
endways  of  the  grain  to  bite  better.  The  section  of  rim  shows  the  shape  to  which  they  are  cut, 
corresponding  to  the  recess  on  the  side  of  wheel,  and  to  the  shrouding  which  is  firmly  bolted  up 
against  them.  The  drums  are  cast  in  segments  and  bolted  together;  the  main  rope  passes  three- 
quarters  round  each  of  them,  describing  a  form  somewhat  resembling  a  figure  8,  and  the  one  end 
leads  clown  to  the  centre  of  the  right-hand  track,  being  in  a  line  with  it,  and  the  other  passes  round 
a  fixed  horizontal  rendering  sheave  of  11  ft.  diameter,  that  being  the  distance  from  centre  to  centre 
of  the  tracks,  which  brings  it  in  centre  of  left-hand  track,  the  ends  being  attached  as  before  men- 
tioned to  the  respective  safety-trucks.  The  working  is  as  follows :  The  loaded  wagons  to  be  raised, 
usually  six  or  seven,  are  pushed  up  to  the  foot  of  the  incline  and  just  in  advance  of  the  tunnel  in 
which  the  safety-truck  is  lying  out  of  sight ;  the  empty  wagons  to  descend  are  run  up  against  the 
other  safety-truck  standing  at  the  head  of  the  incline,  the  engine  is  started,  the  empties  begin 
the  descent,  and  the  safety-truck  emerges  from  the  tunnel  and  pushes  the  loaded  wagons  to  the  top 
of  grade,  where  they  are  shuntod  out  of  the  way,  and  the  empties  run  against  it  ready  for  descent, 
while  the  full  ones  are  also  being  pushed  up  to  position  at  the  foot  of  grade,  the  empty  ones  there 
having  been  removed  to  a  siding. 

"The  heaviest  load  raised  in  one  trip  is  95  tons,  including  cars  and  contents,  but,  of  course,  it  is 
partly  balanced  generally  by  descending  empties.  The  number  raised  from  the  valley  to  the  top  of 
Broad  Mountain,  over  the  two  Gordon  planes,  is  about  90  per  hour.  In  one  month  in  1876  49,000 
loaded  cars  were  raised.  There  are  extensive  sidings  for  the  accommodation  of  a  large  number  of 
loaded  and  empty  wagons  at  the  head  of  the  plane  and  in  the  valley.  For  shifting  the  wagons  and 
forming  the  trains  pushing  engines  are  used." 

Fig.  2381  represents  an  elevation  of  the  winding  engine,  and  Fig.  2382  shows  the  inclination  of 
the  plane. 

"  From  the  altitude,  length,  and  other  particulars  of  the  Mahanoy  plane  given  in  the  table,  it  will 
be  seen  that  it  is  much  shorter,  but  also  steeper,  part  of  it  rising  1  in  4,  than  those  previously 
described.  About  125  loaded  cars  per  hour  are  raised  from  valley  to  topjof  Broad  Mountain,  over- 
coming an  elevation  of  353  ft.  in  about  2,400;  the  number  of  cars  per  trip  is  fewer,  the  maximum 
weight  of  train,  including  cars,  being  about  60  tons — this  made  up  by  the  greater  rapidity  with  which 
the  plane  is  worked,  the  speed  being  at  the  rate  of  nearly  20  miles  per  hour.  The  general  arrange- 
ment of  rails,  safety-trucks,  etc.,  is  similar  to  those  of  the  Gordon.  The  main  rope  is  of  steel,  but 
of  the  same  size  and  style  of  construction  and  tonnage  capacity  as  at  Gordon.  The  engines  are  more 
powerful ;  diameter  of  cylinder  32  in.,  with  7  ft.  stroke.     The  two  main  drums  are  14  ft.  diameter, 



and  have  oak  blocks  grooved  for  the  rope  on  each  side  with  the  teeth  in  centre,  as  per  drawing  of 
section  of  rim,  Fig.  2383,  the  rope  passing  twice  round  each  drum  instead  of  once  as  at  the  Gordon. 
This  is  rendered  necessary  to  prevent  slip  at  the  high  speed  at  which  they  are  run.  Fig.  2383  clearly 
illustrates  this  arrangement.  At  1  is  the  back  rendering  sheave  ;  2,  main  drums  ;  3,  sheaves  to  change 
alignment  of  rope  atTdrunis :  4,  sheaves  at  top.     Fig.  2384  is  a  section  of  main  drum  at  A. 

"  The  fixed  rendering  drum  in  rear  of  engine-house  is  14  ft.  6  in.  diameter,  and  the  movable  one 
for  the  tail  rope  at  foot  of  plane  10  ft.  3  in.  diameter.  As  an  example  of  the  work  this  machinery  is 
capable  of  doing,  during  the  busy  season  of  1876  it  raised  from  the  valley  to  the  summit  an  average 
of  16,000  tons,  including  weight  of  cars,  for  each  working  day." 

Inclined  Planes  on  Canals. — On  the  Morris  and  Essex  Canal  the  construction  of  the  inclined  plane 

is  commonly  as  follows  :  A  track  of  heavy  rails  is  laid  on  the  plane,  which  has  a  grade  of  about  15°, 
and  on  this  the  cradle  containing  the  boat  ascends  at  the  rate  of  five  or  six  miles  an  hour.  At  the 
summit  is  the  motor,  consisting  of  a  water-wheel  driven  by  the  water  on  the  upper  level.  The  wheel 
in  connected  "to  a  shaft  carrying  a  drum  on  which  is  wound  a  wire  rope  about  2  inches  in  diameter, 
which  contains  the  boat,  and  which  forma  a  car  for  its  conveyance.     This  car  is  a  heavy  frame  run- 

ning on  flanged  wheels,  and  descends  a  sufficient  distance  into  the  water  to  enable  a  boat  to  float  into 
it,  where  being  secured  the  car  and  boat  ascend  or  descend  the  inclined  plane  together.  From  the 
forward  end  of  the  car  the  wire  rope  passes  over  anti-friction  rollers,  between  the  rails  of  the  track, 
to  and  around  a  large  submerged  wheel  some  100  feet  distant  from  the  summit ;  thence  over  the 
drum  and  other  friction  rollers  by  the  side  of  the  track  to  another  submerged  wheel  at  the  foot  of 


the  plane,  around  which  it  passes,  and  is  attached  to  the  rear  end  of  the  car.  The  boat  is  made  in 
sections,  to  enable  it  to  accommodate  itself  to  the  inequalities  of  the  track  when  passing  over  the 

Arriving  at  a  plane,  the  boat  is  drawn  into  the  car  in  the  order  of  its  arrival,  the  team  is  unhitched, 
the  boat  secured  in  the  car  by  hawsers,  and  its  two  sections  disconnected.  The  engine  is  then  started. 
After  passing  the  summit  the  brakes  are  put  on,  and  the  car  descends  into  the  water,  where  the  boat 
floats  out  of  it,  and  the  tow-rope  is  again  attached.  In  one  place  the  above-named  canal  has  a  fall 
of  200  feet,  80  of  which  are  overcome  by  a  single  plane  800  feet  in  length,  and  the  remainder  by 
means  of  locks. 

INCRUSTATION.     See  Boilers,  Steam. 
INCUBATOR.     See  Agricultural  Machinery. 

INDIA-RUBBER,  or  CAOUTCHOUC.  The  inspissated  milky  juice  of  a  number  of  trees  and 
plants  found  in  Mexico  and  Central  America,  in  Brazil,  Guiana,  and  Peru,  and  in  the  East  Indies. 
The  Jatropha  elastica  (Linn.)  of  Brazil,  which  flourishes  abundantly,  and  the  Centra]  American  trees, 
furnish  the  greatest  quantities  of  rubber  to  commerce.  The  terms  by  which  the  material  is  known 
in  manufacture  are  Para,  Madagascar,  Guayaquil,  Borneo,  West  India,  Assam,  etc.,  after  the  places 
where  it  is  grown.     The  mode  of  obtaining  rubber  is  as  follows : 

The  trunk  of  the  tree  is  pierced,  and  the  sap  (which  contains  about  40  per  cent,  of  India-rubber) 
is  allowed  to  run  off  into  a  vessel,  but  more  frequently  into  a  hole  dug  at  the  foot  of  the  tree.  Balls 
of  dried  clay  made  in  the  shape  of  pears  are  plunged  into  the  liquid,  and  afterward  passed  over  a 
Are  made  of  the  branches  of  trees,  in  order  that  the  layer  of  India-rubber  which  has  been  deposited 
on  the  clay  may  be  made  to  coagulate  rapidly.  This  operation  is  repeated  until  a  certain  thickness 
has  been  acquired.  The  balls  are  then  plunged  into  water,  and  the  clay,  thus  softened,  is  easily  got 
rid  of  liy  simple  pressure.  Sometimes  a  thin  board  is  used  as  a  nucleus, on  which  the  sap  is  deposited 
and  agglomerated  ;  in  this  ease,  the  mass  of  India-rubber  thus  collected  is  cut  on  three  sides  to  admit 
of  the  board  being  drawn  out,  and  in  this  way  double  sheets  are  obtained,  which  open  almost  in  the 
same  way  as  a  book.  The  purest  India-rubbers  are  those  which  are  {lathered  in  this  way,  such  as 
Para  and  Madagascar,  the  simple  aspect  of  which  reveals  the  almost  total  absence  of  extraneous 
matter.  When  the  sap  is  allowed  to  run  out  on  the  ground,  it  collects  in  irregular  strips,  mixing 
with  the  impurities  of  the  soil.  These  strips  are  put  into  Backs  and  Benl  olF  to  the  various  places  of 
consumption.  When  they  are  very  thin,  they  are  rolled  up  like  a  skein  of  thread,  and  the  appear- 
ance of  the  India-rubber  in  balls  serves  to  remind  one  of  a  clue  of  wot 

The  method  of  preparing  the  crude  rubber  varies.  One  process  consists  in  softening  the  raw  mate- 
rial in  hot  water,  cutting  it  into  pieces  of  about  \\  cubic  inches  by  saws,  and  flattening  it  between 
two  cylinders,  placed  horizontally,  the  distance  between  which  is  regulated  at  will  by  set-screws. 
These  cylinders  are  of  different  velocities;  it  follows,  therefore,  that,  independently  of  the  pressure 
which  the  India-rubber  is  made  to  undergo,  it  is  hacked  and  torn  to  such  an  extent  that  all  extra, 
neons  matters  arc  removed,  and  under  the  continuous  action  of  a  stream  of  water  they  are  easily 
carried  off.  Under  this  process,  which  is  repeated  eight  or  ten  times,  every  time  bringing  the  two 
cylinders  nearer  together,  all  the  impurities  vanish,  and  the  rubber  assumes  the  form  of  an  irregular 
sheet,  grained,  and  pierced  through  with  innumerable  holes.  This  sheet,  when  hung  up  to  dry  in  a 
place  where  the  air  circulates  freely,  thanks  to  its  texture,  very  soon  loses  the  water  with  which  it  is 

The  kneading  is  then  done  in  a  "devil,"  which  consists  of  a  cylinder  fixed  horizontally,  divided  or 
not  into  separate  compartments  by  partitions  perpendicular  to  the  axis.  Over  the  total  length  of 
this  cylinder,  and  a  quarter  of  its  circumference,  there  is  an  opening  by  a  sort  of  door  on  hinges, 
through  which  the  dried  rubber  is  introduced.  A  shaft,  provided  with  a  series  of  sharp-pointed  teeth 
disposed  in  rows  alternating  one  with  another,  ruhs  through  the  whole  length  of  it.  This  shaft, 
which  makes  seven  or  eight  revolutions  a  minute,  carries  along  with  it  the  grained  sheet,  and  causes 
it  to  traverse  the  entire  free  space  of  the  cylinder.  In  doing  this  the  mass  of  caoutchouc  takes  a 
rotating  motion,  produced  by  the  teeth,  which  successively  take  it  up  and  draw  it  toward  them.     There 

results  from  this  a  perfect  process  of  trituration, 
which  forms  the  sheet  of  rubber  into  a  compact 
mass.  It  then  passes  between  steam-heated  com- 
pressing cylinders,  in  which  it  is  compressed  until 
it  presents  the  aspect  of  a  rolled-up  sheet  of  firm 
texture,  close  and  exceedingly  smooth.  This  gives 
the  finish  to  the  preceding  operations. 

The  most  approved  method  of  treatment,  how- 
ever, and  the  one  in  general  use  in  this  country, 
consists  first  in  softening  the  rubber  in  large  tanks 
of  boiling  water.  A  mass  weighing  from  10  to  20 
lbs.  is  then  thrown  upon  a  pair  of  strong  fluted 
cast-iron  cylinders,  between  which  it  is  masticated 
into  small  pieces  and  washed  by  streams  of  hot 
water  which  fall  upon  it  from  a  perforated  horizon- 
tal pipe.  After  being  passed  several  times  through 
the  machine,  it  is  taken  to  another,  similar  in  con- 
struction (Fig.  2385),  but  having  a  pair  of  smooth 
cylinders  in  place  of  the  fluted  ones.  These  produce  an  enormous  pressure,  which  packs  the  pieces 
together  in  the  form  of  a  mat ;  this  is  also  passed  several  times  in  succession  through  the  machine 
and  washed  by  the  dripping  of  hot  water,  as  in  the  preceding  operation.  When  the  mat  is  suffi- 
ciently compacted  and  washed,  it  is  taken  to  a  drying  room,  a  warm  chamber  heated  by  steam,  where 


it  is  allowed  to  remain  from  four  to  six  weeks,  until  it  is  thoroughly  dry  :  for  if  it  were  attempted  to 
work  the  material  while  it  contained  any  moisture,  an  inferior  fabric  would  be  the  result. 

Pure  India-rubber  is  used  only  for  special  purposes.  The  requirements  of  industry  demand  vari- 
ous qualities  of  products,  possessing  properties  suitable  to  the  different  uses  to  which  they  are 
applied.  It  is  the  mixture  of  blocks  of  compressed  rubber  with  foreign  matters  which  enables  the 
manufacturer  to  produce  qualities  answering  to  the  variable  conditions  under  which  they  have  to  be 
used.  Rolling  forms  a  mixture  of  these  several  substances  which  is  regular  and  uniform  through- 
out ;  it  is  also  during  this  operation  that  the  material  for  imparting  any  desired  color  is  added  in  the 
form  of  powder.  When  the  rubber  is  not  rolled,  it  is  moulded  ;  the  paste  being  placed  in  a  mould, 
which  is  exposed  to  a  temperature  varying  between  125°  and  150°.  The  material  is  thus  caused  to 
expand  and  penetrate  into  every  part  of  the  mould.  If  a  hollow  article  is  required,  a  little  water  is 
introduced,  which,  being  changed  into  vapor  by  the  heat,  compresses  the  paste,  and  makes  it  adhere 
to  the  sides  of  the  mould,  of  which  it  takes  the  exact  outline. 

When  rubber  has  been  agglomerated  in  a  "  devil,"  the  mass  is  sometimes  rolled  between  cylinders, 
and  several  thick  sheets  thus  obtained  are  compressed  by  hydraulic  pressure  into  blocks,  which  arc 
cut  up  into  sheets.  For  this  purpose  the  block  of  rubber  is  held  in  movable  bearings,  and  the  cut- 
ting knife  is  carried  in  a  slide.  The  knife  is  kept  continually  wet.  The  sheet  of  rubber,  as  it  is  pro- 
duced by  the  action  of  the  knife,  is  passed  over  and  under  guide-rollers,  and  over  a  drawing  or  taking- 
up  roller,  which,  revolving  and  being  covered  with  India-rubber,  has  sufficient  bite  or  hold  on  the 
sheet  to  draw  it  forward  with  the  required  tension.  The  speed  of  the  roller  is  required  to  decrease 
with  the  size  of  the  block  of  rubber  under  operation ;  for  as  the  sheet  is  cut  from  it  less  length  is 
produced  during  each  revolution  of  the  block,  and  as  it  decreases  in  circumference,  its  rotatory  speed 
being  the  same,  the  roller  in  contact  with  it  will  be  driven  slower,  and  will  communicate  its  decreas- 
ing velocity  by  means  of  the  crossed  straps  to  the  taking-up  roller,  so  that  the  sheet  of  India-rubber 
will  be  taken  up  as  it  is  produced  and  deposited  in  folds  in  front  of  the  machine. 

Raw  India-rubber  seems  to  consist  of  two  parts,  each  possessing  distinct  properties :  the  one  com- 
pact and  elastic,  the  other  heavv  and  semi-liquid.  It  is  to  the  presence  of  the  latter  element  that  is 
to  be  attributed  the  extreme  facility  of  adhesion  by  which  it  is  characterized,  and  it  serves  to  explain 
the  way  it  is  affected  by  the  action'of  the  cold,  and  the  modification  it  undergoes  under  the  influence 
of  a  high  temperature.  The  transformation  of  the  viscous  part,  which  is  most  sensitive  to  the  varia- 
tions of  heat,  has  the  effect  of  preventing  those  grave  inconveniences  arising  out  of  it,  and  of  mak- 
ing India-rubber  a  substance  that  can  be  utilized  under  any  conceivable  circumstances.  That  is  the 
object  attained  by  vulcanization. 

The  agent  employed  for  vulcanizing  is  sulphur.  Its  action  on  India-rubber  is  similar  to  that  on 
fatty  substances,  which,  when  mixed  with  it  in  the  proportion  of  one  to  five,  and  heated  by  a  tem- 
perature of  about  200',  produce  a  substance  offering  a  good  deal  of  resistance,  and  presenting  almost 
the  aspect  of  India-rubber.  The  result  is  that  vulcanized  rubber  does  not  harden  with  the  cold,  nei- 
ther does  it  soften  with  the  heat ;  it  preserves  its  elasticity,  resists  acids,  and  can  no  longer  be  made 
either  to  dissolve  or  to  adhere. 

The  usual  method  of  vulcanization  and  treatment  in  connection  therewith  is  as  follows :  After  the 
sheets  are  prepared  as  described  by  the  masticating  and  compressing  machines,  and  are  thoroughly 
dried,  they  are  passed  successively  through  three  mills.  All  the  mills  are  of  similar  construction  to 
the  one  already  represented,  except  that  in  each  machine  one  cylinder  is  made  to  revolve  twice  as 
rapidly  as  the  other,  in  consequence  of  which  the  material  is  thoroughly  ground  and  mixed.  But 
while  undergoing  the  process  the  continuity  of  the  mat  is  not  destroyed,  for  it  retains  its  form, 
although  a  careful  scrutiny  will  show  that  a  constant  and  rapid  change  of  position  is  going  on  among 
the  particles.  The  cylinders  are  hollow  and  are  supplied  with  steam,  which  keeps  them  at  about 
220°  F.  in  the  first  mill,  and  at  a  little  lower  temperature  in  the  other  two.  The  first  mill  merely 
works  and  compresses  the  material  into  a  firm  thick  sheet  of  a  homogeneous  texture,_  preparatory  to 
the  incorporation  of  the  sulphur  and  whatever  other  ingredients  are  to  be  added,  which  operation  is 
performed  entirely  in  the  second  mill. 

Taking  as  an  example  the  manufacture  of  India-rubber  hose  for  steam  fire  engines,  as  carried  on 
at  a  large  establishment  in  New  York,  the  subsequent  steps  are  as  follows:  After  leaving  the  first 
mill,  about  5  per  cent,  of  sulphur  (and  in  some  cases  certain  mineral  matters,  as  white  lead)  is  thrown 
upon  the  sheet  while  it  is  passing  down  between  the  cylinders.  The  mixing  at  first  causes  disintegra- 
tion and  the  separation  of  the  material  into  shreds ;  but  union  is  speedily  reestablished,  and  the 
mass  again  becomes  homogeneous,  and  will  retain  its  pliability  and  elasticity  after  cooling.  This, 
however,  is  not  allowed  to  take  place  until  it  is  passed  through  the  third  or  finishing  mill.  Herethe 
sheet  is  passed  between  the  cylinders  over  and  over  again,  until  its  pliability  and  working  qualities 
are  perfected,  and  as  far  as  possible  adapted  to  being  spread  upon  canvas.  This  operation  is  per- 
formed in  an  adjoining  room  upon  a  calender  (Fig.  2386),  a  machine  somewhat  similar  to  that  used 
in  cotton-bleaching  establishments.  The  rubber  is  first  of  all  again  passed  through  apair  of  cylin- 
ders in  a  machine  called  a  feeder,  which  is  also  similar  to  the  mills  through  which  it  has  already 
passed.  This  feeder  stands  near  the  calender,  and  its  purpose  is  to  knead  and  temper  the  India- 
rubber  to  the  exact  condition  in  which  it  can  be  best  applied  to  the  cloth.  It  is  taken  in  handfuls  at 
a  time  and  fed  to  the  calender  between  the  two  upper  cylinders  represented  in  the  figure,  but  upon 
the  opposite  side  to  that  which  is  shown.  The  surfaces  of  the  two  cylinders  are  so^  prepared  that 
the  rubber  adheres  in  a  thin  sheet  to  the  lower  one  of  the  two,  which  in  its  revolution  brings  it  in 
contact  with  the  third  or  next  lower  cylinder,  over  which  the  cloth  is  being  passed,  forcing  it  thor- 
oughly into  the  meshes  of  the  fabric.  After  one  side  of  the  canvas  has  been  coated  it  is  turned,  and 
the  rubber  is  applied  to  the  other  side.  It  is  then  taken  to  a  larger  calender,  where  another  coating 
is  applied  to  one  side,  the  whole  sheet  being  well  consolidated  under  powerful  pressure. 

The  cloth  is  now  ready  to  be  made  into  hose,  and  the  operation  is  commenced  by  cutting  it  into 



strips  diagonally,  so  that  both  warp  and  weft  may  receive  the  strain  to  which  the  hose  may  be  sub- 
jected, thus  greatly  increasing  the  strength  of  the  fabric.  The  strips  are  cut  in  width  a  little  more 
than  twice  the  intended  circumference  of  the  hose,  so  that  one  sheet  will  form  two  thicknesses 
of  its  walls.     The  inner  layer  of  the  pipe  is  formed  by  a  thick  sheet  of  uncanvascd  vulcanized 


rubber,  which  has  been  also  prepared  in  one  of  the  calenders.  This  is  cut  of  the  proper  width,  and 
wound  round  a  long  iron  pipe  used  as  a  mandrel,  and  its  edges  are  lapped  over  one  another,  firmly 
pressed  together,  and  permanently  joined  by  a  small  grooved  roller  held  in  the  hand  of  the  workman. 
Before  bring  applied,  the  inner  surface  of  this  sheet  of  robber  must  be  coated  over  with  a  powder  of 
some  substance  winch  will  prevent  adhesion  to  the  mandrel,  so  that  it  may  be  removed  after  the 
hc-c  is  finished.  The  best  substance  is  soapstone,  or  steatite.  The  lapping  edge  must  be  carefully 
left  untouched  with  this  material,  or  perfect  union  will  not  be  possible.  Around  this  inner  coating 
are  now  successively  wrapped  two  strips  of  the  bias-cut  rubber  canvas,  and  over  this  another  and 
outer  coat  of  pure  vulcanized  robber,  making  six  coats  in  all,  four  of  which  are  of  rubber  canvas. 
It  is  claimed  that  hose  of  2  in.  calibre,  made  in  this  manner,  is  capable  of  resisting  a  hydrostatic 
pressure  of  400  lbs.  per  square  inch  at  a  temperature  of  60  P.  Each  length  of  hose  is  usually 
made  50  ft.  long,  which  has  been  found  the  most  convenient  for  use  on  the  hose  carriages,  the 
lengths  being  joined  as  required  by  couplings.     After  every  layer  has  been  wound  over  its  concentric 

fellow,  and  also  during  the  process,  the  work- 
men make  use  of  their  rollers  to  compress  and 
consolidate  the  hose.  After  all  the  layers  have 
been  applied,  the  pipe  is  taken  to  another  bench, 
where  it  is  covered  with  four  or  five  layers  of 
cotton  cloth,  and  then,  with  several  others,  it  is 
placed  upon  a  long  carriage  which  runs  upon 
rails  into  a  large  hollow  cylinder,  Fig.  23S7, 
which  is  heated  by  live  steam,  or  steam  which 
is  not  superheated,  coming  immediately  from  the 
boiler,  and  usually  at  a  pressure  which  will  give 
it  a  temperature  of  about  240^  F.  When  the 
rubber  has  been  confined  in  this  cylinder,  at  this 
temperature,  for  eight  or  ten  hours,  the  true  vul- 
canization or  union  of  the  caoutchouc  with  the 
sulphur  takes  place,  accompanied  with  the  dis- 
engagement of  sulphuretted  hydrogen  gas.  This 
is  one  of  the  most  important  parts  of  the  pro- 
cess of  manufacture,  and  upon  it,  as  well  as 
upon  the  mixing  of  the  ingredients,  depend  the 
strength  and  elasticity  of  the  product.  The  heat 
should  be  raised  gradually  and  maintained  at  a 
determined  point  till  the  vulcanization  is  com- 
pleted, and  then  should  lie  immediately  withdrawn.  In  manufacturing  engine  hose,  the  New  York 
Grutta  Percha  and  Rubber  Manufacturing  Company  mix  a  certain  amount  of  carbolic  acid  with  the 
caoutchouc,  which  it  is  claimed  preserves  the  hose  and  shortens  the  process  of  vulcanization.  An 
ingenious  register  is  in  use  at  their  factory,  the  invention  of  Mr.  John  Murphy,  by  which  the  appli- 



cation  of  a  steam-pressure  gauge  to  clockwork  records  the  different  degrees  of  temperature  and  their 
duration  which  may  have  been  reached  during  the  vulcanizing  process,  which  is  generally  performed 
during  the  night,  under  the  care  of  one  or  two  men. 

When  caoutchouc  is  intended  for  car  springs,  about  5  per  cent,  of  white  lead  and  variable  propor- 
tions of  carbonate  of  lime  are  added,  with  5  per  cent,  of  sulphur.  This  makes  the  product  more 
solid  and  substantial,  and  capable  of  supporting  greater  weight  without  too  much  compression, 
which  is  objectionable.  In  the  manufacture  of  ebonite,  a  much  larger  proportion  of  sulphur  is  used ; 
and  in  the  cheaper  kinds,  when  great  strength  is  not  required,  various  earthy  substances  are  employed. 
But  sulphur  and  caoutchouc  alone,  when  properly  mingled  and  raised  to  the  required  degree  of  heat, 
produce  the  best  article.  The  temperature  necessary  to  effect  the  proper  result  varies  with  the  pro- 
portion of  the  ingredients,  and  ranges  from  250°  to  something  over  300°,  this  also  being  more  or  less 
modified  by  the  time  employed. 

When  India-rubber  is  woven  into  fabrics,  it  is  prepared  for  the  purpose  by  slicing  it  into  threads, 
with  knives  worked  by  machinery  and  kept  wet.  These  threads  are  wound  upon  cylinders  in  a 
state  of  tension,  and  are  woven  into  the  fabric  in  this  condition.  In  the  early  manufacture  of  fabrics 
of  this  kind  a  process  technically  called  "  shirring  "  was  employed.  The  elastic  threads,  in  a  state  of 
tension,  were  passed  between  rollers,  and  then  between  two  other  rollers  over  each  of  which  was 
passed  a  strip  of  cloth,  cotton,  or  silk.  This  brought  the  threads  between  the  two  layers  of  cloth, 
and  the  latter  having  been  prepared  with  a  coating  of  India-rubber  cement,  they  were  held  there. 
One  of  these  shirring  machines,  together  with  a  machine  for  cutting  the  threads,  was  the  invention  of 
James  Bogardus  of  New  York,  and  was  extensively  used  for  a  number  of  years.  The  goods  made 
by  that  process  have  however  entirely  given  place  to  woven  fabrics  ;  and  the  cutters  now  used  are 
single  circular  knives,  revolving  with  high  speed,  cutting  6heets  wound  upon  cylinders,  which  are 
given  a  slow  rotary  as  well  as  a  side  motion,  by  which  the  thread  is  cut  in  a  spiral. 

INDICATOR.  The  steam-engine  indicator  is  a  device  for  recording,  by  means  of  a  diagram,  the 
successive  pressures  in  a  steam-cylinder  at  every  point  of  the  double  stroke.  It  is  also  used  similarly 
to  measure  the  pressures  in  the  cylinders  of  air,  gas,  and  water  engines  and  pumps.  The  principles 
of  the  construction  and  operation  of  an  indicator  will  be  understood  by  referring  to  Fig.  2388,  in 
which  A  B  represents  the  cylinder  of  a  steam-engine,  C  the  piston,  and  D  the  piston-rod  of  the 


same  connected  to  the  load  through  the  connecting-rod  E,  crank  F,  and  shaft  G,  as  sketched,  or  in 
any  customary  manner.  The  remainder  of  the  figure  shows  the  principal  features  of  an  indicator  on 
an  enlarged  scale,  though  modified  slightly  in  detail  to  facilitate  explanation.  H  is  the  indicator- 
cylinder,  which  is  connected  to  the  end  A  of  the  main  cylinder  through  a  short  passage  regulated  by 
a  cock  a,  which  is  so  constructed  as  to  put  the  indicator-cylinder  in  communication  with  the  atmos- 
phere when  the  passage  to  main  cylinder  is  closed.  Suitable  openings  are  provided  to  keep  the 
upper  part  of  the  indicator-cylinder  in  communication  with  the  atmosphere  at  all  times.     /  is  the 


indicator-piston,  which  is  connected  to  one  end  of  a  spiral  spring,  the  other  end  of  which  is  held 
stationary  in  any  suitable  manner.  if  is  a  pencil,  which  is  moved  up  and  down  by  the  piston  /,  either 
by  a  direct  connection  through  a  piston-rod  b,  as  shown,  or  through  a  system  of  levers.  The  pencil  is 
adjusted  to  bear  lightly  upon  a  piece  of  paper  L,  which  is  secured  to  a  slide  M,  receiving  a  lateral 
movement  from  the  main  piston  through  the  lever  N  and  links  c  and  e,  as  shown.  Usually,  however, 
the  paper  is  secured  to  a  drum,  which  is  partially  revolved  back  and  forth  by  levers,  cords,  and  a 
spring  hereafter  described,  which  impart  to  the  paper  the  reduced  movement  of  the  main  piston  in  the 
same  or  the  opposite  direction.  The  compressions  or  extensions  of  accurately  constructed  springs  are 
proportioned  to  the  intensities  of  the  forces  impressed ;  hence,  if  the  resistance  of  the  spring  of  the 
indicator  be  such  that  it  will  require  15  lbs.  to  compress  it  one  inch,  and  the  piston  /  have  an  area 
of  one  half  inch,  the  pencil  will  be  moved  one  inch  by  a  pressure  of  30  lbs.  per  square  inch  on  the 
piston,  and  proportionally  for  other  pressures.  In  such  case  the  scale  of  the  indicator  is  called  30  lbs. 
per  inch,  or  the  spring  is  marked  ■,',;,  meaning  that  the  movement  is  one-thirtieth  of  an  inch  for  each 
pound  pressure  per  square  inch  on  piston.  Indicators  are  usually  provided  with  several  springs  of 
different  strengths — scales  of  10  lbs.  per  square  inch  being  used  for  low-pressure  air-engines,  scales 
from  16  to  32  lbs.  per  square  inch  for  ordinary  low-pressure  condensing  engines,  and  of  40  to  60  lbs. 
or  more  for  high-pressure  engines. 

Referring  to  Fig.  2388,  if  the  engine  be  in  operation  and  the  cock  a  shut,  the  atmospheric  pres- 
sure will  be  on  both  sides  of  the  piston  as  previously  explained,  and  the  piston  and  pencil  in  position 
opposite  the  point  marked  0  on  the  scales  shown,  when,  by  the  lateral  movement  of  the  paper, 
the  line  (//will  be  traced,  called  the  atmospheric  line.  When  the  cock  a  is  turned  to  admit  steam 
from  the  main  cylinder  A  to  the  indicator,  the  piston  of  the  latter  will  be  forced  up  and  down;  and 
this  movement,  combined  with  the  lateral  motion  of  the  paper,  will  cause  the  pencil  to  trace  a  dia- 
gram in  which  the  vertical  height  above  the  atmospheric  line  at  any  point  will  represent  the  pressure 
in  the  main  cylinder  at  the  portion  of  the  stroke  corresponding  to  the  horizontal  position  of  the 
point.  For  instance,  if  the  main  piston  be  at  position  1,  or  just  commencing  its  stroke,  line  1  on  paper 
/,  will  be  opposite  pencil  K.  If  steam  of  60  lbs.  pressure  be  then  admitted  to  the  main  and  indica- 
tor cylinders,  the  pencil  will  be  carried  up  to  the  point  g  opposite  60  on  the  scale  at  the  left.  If  the 
steam  remains  at  60  till  the  main  piston  reaches  position  2,  line  2  on  the  paper  will  be  moved 
opposite  the  pencil,  and  the  latter  remaining  stationary  will  trace  the  line  (/A.  If  the  steam  be  now 
cut  off,  the  pressure  in  the  main  cylinder  will  fall  rapidly,  and  by  the  time  the  main  piston  reaches 
position  S  the  paper  will  be  in  the  position  shown,  and  the  pencil  will  have  dropped  to  i,  or  opposite 
about  27  lbs.  on  the  scale  of  pressures  as  shown,  tracing  in  its  downward  movement,  combined  with 
that  of  the  paper,  the  curve  h  i.  the  height  of  which  at  any  point  shows  the  pressure  in  the  main 
cylinder  at  the  eon  .-ponding  portion  of  the  stroke.  The  pressure  will  gradually  fall  in  the  cylinder 
as  the  piston  advances,  and  the  curve  ijk  be  traced  on  the  diagram.  At  or  near  /■  the  steam  will 
be  exhausted  and  the  pencil  fall  to  p,  showing  a  back  pressure  of  about  1|  lb.,  which  may  remain 
nearly  constant  while  the  main  piston  is  passing  the  positions  6,  7,  and  8  on  the  return  stroke, 
so  that  the  pencil  will  trace  the  linejDO.  If  at  othe  exhaust-port  be  shut,  the  back-pressure  vapor 
will  be  compressed  and  the  pressure  rise,  forming  the  curve  ou;  and  about  the  time  the  piston 
reaches  the  end  of  the  stroke  steam  will  be  again  admitted  and  force  the  pencil  to  g,  tracing  line  ug, 
and  the  operations  be  repeated.  If  there  be  a  vacuum  in  the  cylinder  during  the  return  stroke,  the 
atmospheric  pressure  will  force  the  piston  /  below  the  point  0  on  the  scale,  and  the  pencil  K  trace 
a  back-pressure  or  vacuum  line  below  the  atmospheric  line,  as  shown  by  the  dotted  line  pi  ox.  The 
vacuum  shown  in  a  steam-cylinder  usually  corresponds  to  a  reduction  of  pressure  of  from  10  to  12 
lbs.  The  theoretical  full-stroke  diagram  is  evidently  a  rectangle.  It  is  however  not  obtained  in 
practice  in  a  steam-engine,  but  is  closely  approximated  in  the  best  pumps. 

Fig.  23S9  is  a  diagram  similar  to  the  one  above  developed,  with  such  modifications  as  are  found  in 
practice.  The  line  df,  which  is  drawn  by  the  instrument,  is  as  before  stated  called  the  atmospheric 
line.  A  line  R  U,  called  the  true  vacuum  'line,  may  be  drawn  on  the  paper  by  hand  at  the  distance 
below  the  atmospheric  line  corresponding  to  the  height  of  the  barometer,  or  usually  14.7  lbs.     A 

line  s  t  is  also  drawn  in  some  cases  to  show  the  pres- 
sure in  the  steam-chest  or  boiler.  The  line  ug  is 
called  the  receiving  line,  and  gh  the  steam  line.  The 
sudden  rise  of  the  indicator-piston  in  drawing  the 
line  ug  often  induces  vibrations  of  the  spring,  mak- 
ing the  steam  line  undulatory,  as  shown  in  dotted 
lines.  At  h  is  the  point  of  cut-off,  which  theoretically 
should  be  a  sharp  angle,  but  in  practice  is  more  or 
less  rounded,  according  to  the  velocity  with  which 
the  cut-off  valve  is  closed.  Usually  also  the  cylin- 
der-ports are  not  of  sufficient  size  to  maintain  the 
initial  pressure  to  the  point  of  cut-off.  The  result 
is  a  kind  of  imperfect  expansion,  shown  by  the  slope 

'  "v»-_jj, fj       of  the  line  from  g  to  h,  which  is  called  wire-dr -awing. 

•^ ■ j^     The  curved  line  h  k  is  called  the  expansion  curve,  and 

k p  or  kpi  the  exhaust  line  or  curve,  k  being  called 
the  point  of  release.  The  line  poona  diagram  from  a  non-condensing  engine,  orpi  ox  from  a  con- 
densing engine,  is  called  the  back-pressure  line  ;  but  the  latter  is  more  generally  called  the  vacuum 
line.  The  curve  o  u  is  called  the  cushion  curve.  Pressures  above  the  atmospheric  line  df  are  called 
pressures  above  the  atmosphere  or  pressures  by  gauge  ;  and  pressures  above  the  perfect  vacuum  line 
R  U  are  called  toted  pressures.  The  pressure  at  the  beginning  of  the  stroke  is  called  the  initicd,  and 
at  the  end  the  terminal  pressure  ;  the  two  latter  may  either  be  total  or  above  the  atmosphere. 



Mariotte's  law  of  the  free  expansion  of  gases  (applicable  strictly  only  to  perfect  gases  expanding 
without  change  of  temperature)  is,  that  the  pressures  are  inversely  as  the  volumes.  It  follows  then 
that  the  products  of  the  pressures  by  the  corresponding  volumes  are  severally  equal  to  a  constant. 
On  this  basis  the  expansion  curve  is  hyperbolic,  an  equation  of  the  hyperbola  being  xy  =  a.  In  the 
practical  operation  of  a  steam-engine,  heat  is  transmuted  into  work,  and  condensation  takes  place  in 
the  cylinder  sufficient  to  supply  one  heat-unit  for  each  772  foot-pounds  of  work.  On  this  basis  the 
pressures  should  decrease  faster  than  the  ordinates  of  a  hyperbolic  curve ;  and  to  express  the  rela- 
tion, an  equation  has  been  developed  for  what  is  termed  the  adiabatic  curve,  in  which  the  heat 
transmuted  into  work  is  considered,  but  no  allowance  is  made  for  transmission  to  and  from  the 
steam  and  its  inclosing  walls.  Inasmuch  as  such  transmission  does  take  place— often  to  an  enor- 
mous extent,  and  always  to  an  important  degree— by  which  means  the  practical  curve  of  expansion  is 
usually  raised  to  or  above  the  hyperbolic  curve,  it  follows  that  the  latter  practically  represents  all 
the  conditions  better  than  the  adiabatic  curve ;  for  which  reason,  and  to  secure  simplicity,  the  hyper- 
bolic curve  will  be  herein  considered  as  the  theoretical  curve  of  expansion. 

For  various  reasons  hereafter  explained,  it  is  desirable  to  lay  down  the  theoretical  curve  upon 
indicator  diagrams  for  the  purpose  of  comparing  it  with  the  indicated  curve,  and  thereby  ascer- 
taining the  condition  of  the  engine.  This  may  be  done  in  several  ways,  two  of  which  will  be 
explained  in  connection  with  Fig.  2390.  The  first  step  is  to  lay  down  the  perfect  vacuum  line  Q  IT 
at  a  distance  below  the  atmospheric  line  df,  by  the  scale  of  pressures  equal  to  the  barometric  pres- 
sures at  the  time,  or  usually  U.I  lbs.     A  perpendicular  Q  Qi  should  also  be  erected  to  lengthen  the 


diagram,  in  the  same  proportion  that  the  spaces  in  clearances  and  passages  increase  the  capacity  of 
the  cylinder.  For  instance,  if  the  clearances,  etc.,  equal  .07  of  the  displacement  of  the  piston  (or  of 
its  area  multiplied  by  the  length  of  stroke),  then  Q  R  =  .07  x  R  IT.  If  it  be  desired  that  the  curve  of 
expansion  pass  through  a  particular  point  of  the  indicated  curve,  z2  for  instance,  by  multiplying  the 
distance  of  z2  from  Q  Qx  in  any  scale  by  the  total  pressure  at  aa  (viz.,  above  Q  U),  the  product 
will  be  a  constant  which,  divided  by  the  distance  of  any  vertical  line  from  Q  Qx  in  the  same  scale 
previously  employed,  will  give  the  total  pressure  at  the  point  where  the  theoretical  curve  crosses  that 
vertical  line.  For  instance,  QS  x  Sz2  -=-  Q  U=  lTzu ;  and  the  points  z10,  z9,  etc.,  may  be  found  in 
a  similar  manner. 

There  are  many  methods  of  laying  down  the  curve  graphically.  The  following  method,  employed 
by  the  writer,  is  quite  simple,  and  avoids  the  necessity  of  dividing  the  diagram  into  equal  parts. 
First  select  any  desired  point  through  which  the  curve  is  to  pass ;  multiply  together  the  distances  of 
that  point  from  the  asymptotes  Q  Qi  and  Q  U  (measuring  the  distances  with  the  same  scale,  that  of 
pressures  preferably) ;  extract  the  square  root  of  the  product ;  lay  off  the  value  of  the  root  from  Q 
to  X  and  Q  to  Y,  and  draw  X  x  and  Yy  parallel  to  the  asymptotes.  Then,  if  from  points  Xi,  x2,  x3, 
etc.,  at  different  portions  of  the  stroke,  on  line  Xx,  diagonal  lines  be  drawn  to  the  origin,  Q,  such 
diagonals,  produced  if  necessary,  will  intersect  the  line  Yy  at  points  showing  the  pressures  at  the 
corresponding  points  of  the  stroke  Xi,  x2,  etc. ;  and  drawing  x±  zh  x*  z2,  etc.,  parallel  with  Q  Q%,  and 
l/i  «i,  yi  22,  etc.,  parallel  with  Q  IT,  the  intersections  zu  z2,  z3,  etc.,  are  points  in  the  theoretical  curve. 
The  square  root  of  the  product  referred  to  may  be  obtained  graphically  by  drawing  zs  S  parallel 
with  Q  Qi,  laying  off  Q  P  equal  to  the  pressure  Sz2 ;  and  drawing  a  semicircle  through  points  P  and 
S,  intersecting  Q  Qi  at  the  point  X,  then  Q  X  equals  the  root  desired ;  and  drawing  quadrant  X  Y 
with  Q  as  a  centre  locates  also  the  point  Y.  The  theoretical  compression  curve  o  r  may  be  laid 
down  in  a  similar  manner,  starting  from  o.  The  practical  compression  curve  generally  falls  below 
the  theoretical  curve,  as  shown  approximately  at  o  u,  on  account  of  condensation  to  reheat  the  cylin- 
der as  pressure  rises. 

In  most  cases,  when  using  saturated  steam  at  short  points  of  cut-off,  the  indicated  expansion  curve 
falls  below  the  theoretical  curve  near  the  beginning  of  the  stroke  (condensation  taking  place  to  reheat 
the  cylinder),  and  rises  above  the  latter  near  the  end  of  the  stroke  (from  re-evaporation),  substan- 
tially as  shown.  With  steam  quite  dry  and  the  better  class  of  engines,  however,  the  indicated  and 
theoretical  curves  agree  very  closely.  With  very  wet  steam  the  indicated  curve  near  end  of  stroke 
rises  considerably  above  a  hyperbolic  curve  run  through  the  point  of  cut-off,  while  with  highly  super- 
heated steam  it  often  runs  a  little  below,  the  same  as  the  adiabatic  curve.     In  vertical  engines, 



when  cutting  off  short,  water  is  likely  to  collect  above  the  piston,  distorting  the  diagram  from  the 
top  of  the  cylinder  by  raising  the  terminal  pressure,  as  shown  in  Fig.  2403. 

Defects  in  the  design  and  adjustment  of  valves  and  valve-gear,  leaks  of  the  valves  or  pistons,  as 
well  as  the  quality  of  the  steam  and  the  thermal  condition  of  the  steam-cylinder,  may  all  be  ascer- 
tained from  indicator  diagrams  which  have  been  carefully  taken  with  a  good  instrument.  When  the 
eccentric  is  too  far  ahead,  the  diagram  shows  an  excess  of  lead,  as  represented  in  Fig.  2391.  Steam 
is  taken  at  u  before  the  end  of  the  stroke,  and  the  receiving  line  ug  is  inclined.  'With  a  slide-valve 
the  point  of  release  k  will  also  be  farther  away  from  end  of  stroke,  showing  an  early  exhaust.  In  loco- 
motives and  rapidly-moving  engines  early  steam  and  exhaust  lead  is  de.-irable,  to  cushion  the  recipro- 
cating parts.  (See  Figs.  2398,  240<>,  and  2401.)  When  the  eccentric  is  behind,  the  steam  and 
exhaust  lines  incline  in  the  opposite  direction,  as  shown  in  Fig.  2392.     Generally,  too,  the  steam  line 




is  lower  than  is  ordinarily  the  case  to  the  point  of  cut-off;  and  for  fixed  cutoff  and  constant  steam- 
pressure,  the  pressure  in  the  cylinder  will  be  less  throughout  the  stroke  than  when  sufficient  lead  is 
given.  When  Bteam  is  wet,  the  steam  line  is  usually  lower  than  usual,  and  the  pressure  at  end  of 
stroke  rises  considerably  above  the  theoretical  curve.  Generally,  too,  the  vacuum  at  the  beginning 
of  the  return  stroke  will  he  reduced,  as  shown  in  Fig.  2393.  If  the  engine  has  independent  Bteam 
and  exhaust  valves,  and  tin-  Bteam-valve  leaks,  the  Bteam  line  will  he  in  its  ordinary  position,  but  the 
expansion  curve  will  he  above  its  true  position,  much  the  same  as  if  the  strain  were  wet.  On  the  con- 
trarv,  if  the  piston  or  the  exhaust-valve  leaks,  both  the  steam  and  expansion  lines  will  he  low;  and 
generally,  hut  particularly  when  the  piston  leaks,  the  hack-pressure  line  "ill  he  high  and  the  vacuum 
low  at  the  beginning  of  the  return  stroke,  a9  shown  in  Fig.  2394 — steam  at  that  time  being  admitted 
at  full  pressure  on  the  other  side  of  the  piston.  Caution  and  experienced  judgment  are  required 
to  distinguish  distortions  of  the  diagram  due  to  wet  steam  from  those  arising  from  misadjustment  of 
the  valves.  When  the  cylinder,  or  part  of  the  same,  is  exposed  to  cold,  or  attached  to  large  masses 
of  metal  so  exposed,  the  diagrams  show  unmistakable  signs  of  moisture,  and  are  of  reduced  area. 

One  of  the  principal  uses  of  the  indicator  is  to  determine  the  power  developed  by  an  engine.     The 
indicator  diagram  shows  the  pressures  in  the  cylinder  at  all  points  of  the  stroke,  and  the  first  step  is 




o<i«jc$   y  «  ^  in  y  ii 

?°     S    go    *?     «    «i    S    *>'     « 

**<o<o       *     f?      ^     «W       C\> 


to  ascertain  the  average  or  mean  effective  pressure.  This  is  usually  accomplished  by  the  general 
method  employed  to  measure  irregular  figures.  Ordinarily  the  diagram  is  divided  into  a  number  of 
equal  parts,  ten  being  customary  and  sufficient  for  most  purposes ;  then  the  pressures  from  bottom 
to  top  of  the  diagram  are  measured  with  the  scale  centrally  between  the  lines,  and  the  sum  of  the 
different  measurements  divided  by  the  number  of  ordinates  gives  approximately  the  mean  pressure. 
It  is  better,  however,  to  make  the  divisions  so  that  a  half  space  occurs  at  each  end,  and  then  measure 
directly  on  instead  of  between  the  lines.  This  can  be  conveniently  done,  when  a  number  of  diagrams 
are  to  be  used,  by  laying  off  the  spaces  on  a  piece  of  card-board  shaped  like  A,  Fig.  2395,  made  a 
little  longer  than  the  average  length  of  the  diagrams,  so  that  it  may  be  conveniently  applied  between 
the  lines  B  C  and  D  E,  which  should  in  all  cases  be  drawn  at  the  ends  of  the  diagram  at  right  angles 
to  the  atmospheric  line.     The  different  points  are  then  to  be  pricked  through,  and  the  division  lines 


drawn  from  the  same  parallel  to  those  at  the  end.  Ten  points  may  be  similarly  arranged  in  a  piece 
of  wood,  and  all  pricked  into  the  paper  at  one  time.  The  multiple  parallel  ruler,  shown  in  two  posi- 
tions in  Figs.  2396  and  2397,  is  furnished  by  the  Messrs.  Elliott  Brothers  with  the  Richards  indicator 
for  a  similar  purpose.  The  parallels  should  first  be  adjusted  to  the  length  of  the  diagram,  and  a  dot 
made  for  the  first  end  division.  This  distance  should  be  bisected  and  the  ruler  moved  bodily  the  half 
space,  without  permitting  motion  in  the  joints,  when  the  ten  parallel  lines  may  be  drawn  across  the 
card  with  half  spaces  at  the  end,  the  same  as  in  Fig.  2395.  The  pressures  by  scale  at  the  several 
points  may  be  conveniently  marked  upon  or  at  the  side  of  the  diagram,  summed  and  divided  by  ten 
as  shewn,  which  will  give  the  mean  pressure.  The  writer  has,  however,  found  it  more  convenient  to 
take  off  the  successive  measurements  on  a  strip  of 
drawing-paper,  using  a  sharp-pointed  knife  to  shift 
a  point  in  the  strip  from  the  bottom  of  one  ordi- 
nate to  the  top  of  the  next.  The  portion  of  the 
strip  used  is  then  measured  in  inches,  and  the  re- 
sult, divided  by  one-tenth  of  the  scale  of  the  indica- 
tor, equals  the  mean  pressure.  This  division  need 
not  be  made  until  the  gross  lengths  of  the  ordinates 
of  all  the  diagrams  have  been  summed  together. 
When  diagrams  from  both  ends  of  the  cylinder  are 
taken  on  the  same  paper,  as  shown  in  Figs.  2398 
to  2406,  the  sum  of  the  ordinates  of  both  may  be 

obtained  on  the  strip  at  one  operation,  in  which  case  the  result  must  finally  be  divided  by  two. 
The  areas  of  diagrams  are  frequently  measured  with  a  planimeter,  in  which  case  the  area  in  square 
inches  and  length  of  diagram  in  inches  and  hundredths  are  simply  to  be  noted,  when  the  sum  of  the 
areas,  divided  "by  the  sum  of  the  lengths  and  multiplied  by  the  scale  of  the  indicator,  equals  the 
mean  pressure.  When  diagrams  are  double,  the  result  should  be  divided  by  two,  or  for  simplicity 
half  the  scale  of  the  indicator  used  for  a  multiplier. 

The  system  of  measuring  from  the  top  to  the  bottom  of  the  same  diagram  above  provided  for 
does  not  show  the  true  effective  pressure  on  the  piston  at  the  position  where  the  measurement  is 
taken.  The  effective  pressure  at  any  position  of  the  piston  evidently  equals  the  pressure  on  one  side 
less  that  on  the  other.  This  can  be  obtained  by  taking  diagrams  from  both  ends  of  the  cylinder  on 
the  same  sheet,  or  combining  the  two,  as  in  Fig.  2398  ;  then  the  effective  pressure  at  any  point  may 
be  found  by  measuring  from  the  top  of  one  diagram  to  the  bottom  of  the  other.  In  the  figure  the 
effective  pressures  are  measured  by  the  successive  heights  of  the  shaded  figure  A  C  E  G,  and  the 
latter  part  of  the  stroke  is  completed  against  the  resistance  of  pressures  measured  by  the  successive 
heights  of  the  figure  D.  The  average  effective  pressure  in  both  ends  of  the  cylinder  will,  however, 
in  all  cases  equal  the  average  mean  pressure  of  the  diagrams  found  in  the  manner  above  explained. 
For,  representing  the  pressures  by  the  areas,  if  we  add  the  areas  included  in  the  figures  represent- 
ing the  actual  mean  effective  pressures  for  both  ends  of  the  cylinder,  viz.,  A  +  C  +  E+  G—D,  and 
B  +  D  +  F+  G—C,  the  sum  reduces  to  A  +  B+2G  +  E+  E,  which  is  the  sum  of  the  areas  of  the  two 
diagrams,  and  will  be,  no  matter  what  their  relative  areas.  The  method  of  measuring  each  diagram 
separately  gives,  therefore,  accurate  final  results ;  and  the  more  complex  system  need  be  adopted  only 
when  for  any  reason  it  is  desired  to  separate  the  work  done  in  one  end  of  the  cylinder  from  that  done 
in  the  other.  In  some  cases  the  steam-pressures  are  measured  from  the  top  of  the  card  to  the  atmos- 
pheric or  perfect  vacuum  line,  and  the  back  pressures  to  the  same  line,  and  the  average  of  the  latter 
subtracted  from  the  former.  This  is  in  general  unnecessary.  By  multiplying  the  area  of  piston  in 
square  inches  by  the  mean  pressure  in  pounds  per  square  inch  obtained  as  above,  the  mean  total  effec- 
tive force  urging  the  piston  is  obtained ;  and  multiplying  this  by  the  speed  of  the  piston  in  feet  per 
minute  gives  the  number  of  foot-pounds  of  work  performed  in  a  minute,  which,  divided  by  33,000 
(which  equals  the  number  of  foot-pounds  per  minute  in  one  horse-power),  gives  the  number  of  horse- 
powers developed. 

In  obtaining  the  area  of  a  piston,  the  area  of  the  piston-rod  should  be  considered.  If  the  piston- 
rod  runs  through  one  end  only  of  the  cylinder,  half  the  area  of  the  rod  should  be  deducted  from  the 
total  area  of  the  piston,  and  the  result  will  be  the  mean  area  of  the  two  sides  of  the  latter.  Let 
P  equal  the  indicated  horse-power,  m  the  mean  pressure  in  the  cylinder  in  pounds  per  square  inch,  A 
area  of  piston  in  square  inches,  S  length  of  stroke  in  feet,  and  J2  number  of  revolutions  per  minute  : 

j4  X  lYl   X  **  X  S  X  H 

then  P  = For  a  triven  engine  the  portion  of  the  above  equation  represented 

33,000  b  fa  i 

by  A  x  2  x  S -=-  33,000  is  always  constant,  and  represents  the  power  developed  by  the  engine  per 
pound  of  mean  pressure  in  the  cylinder  for  each  revolution  per  minute.  It  is  the  habit  of  the 
writer  to  ascertain  this  constant  in  the  first  instance,  and  keep  a  memorandum  of  it  in  connec- 
tion with  the  dimensions  of  the  engine,  when  at  any  time  the  power  may  be  ascertained  by  simply 
multiplying  together  the  constant,  the  mean  pressure,  and  the  revolutions  per  minute.  Putting 
K=  such  constant,  D  =  diameter  of  cylinder,  d  =  that  of  the  piston-rod,  and  re  =  3.1416;  then 

K  =  2S     ir  (  —  J  -  ^-f  —  J     U-  33,000  =  -0000238  (iD2-  d2  \  S,  and  P  =  K  m  R. 

Thus,  for  a  cylinder  34.1  inches  in  diameter,  with  piston-rod  4|  inches  in  diameter,  and  30  inches  or 
2.5  feet  stroke  of  piston,  A^=  .13723.  So,  when  the  mean  pressure  is  30  lbs.,  and  the  engine  making 
70  revolutions  per  minute,  the  horse-power  P  =  .13723  x  30  x  70  =  288.183. 

The  approximate  quantity  of  steam  used  by  an  engine  may  also  be  determined  from  an  indicator 
diagram.     To  do  this,  it  is  necessary  to  ascertain  the  specific  volumes  or  weights  per  cubic  foot  of 



steam  at  different  pressures.  These  are  tabulated  in  works  on  the  subject.  Referring  to  Fig.  2390, 
the  cylinder  to  the  point  of  cut-off  h,  including  the  clearance  spaces,  is  full  of  steam  at  the  total  pres- 
sure *S7t.  The  size  of  cylinder  and  point  of  cut-off  being  known,  it  is  easy  to  find  the  number  of  cubic 
feet  included  in  the  cylinder  to  that  point,  including  the  average  clearance  spaces  for  the  two  ends  of 
the  cylinder,  which,  multiplied  by  the  number  of  strokes  per  hour,  will  give  the  number  of  cubic  feet 
of  steam  of  that  pressure  used  per  hour;  and  the  latter  quantity,  multiplied  by  the  weight  of  a  cubic 
foot  of  steam  at  that  pressure,  equals  the  calculated  weight  of  steam  per  hour.  The  amount  of  steam 
required  from  the  boiler  is,  however,  less  than  this,  as  the  clearance  spaces  during  each  stroke  are 
filled  with  steam  of  the  final  total  cushion  pressure  A'w,  so  that  the  capacity  of  the  clearance  in  cubic 
feet  multiplied  by  the  number  of  strokes  per  hour,  and  by  the  weight  of  a  cubic  foot  of  steam  at  the 
total  pressure  A'",  must  be  deducted  from  the  previous  result, and  the  remainder  represent  the  calcu- 
lated weight  of  water  that  must  be  evaporated  per  hour  to  produce  the  power.  The  calculation  may 
in  like  manner  be  made  for  the  volume  and  pressure  at  any  other  point  in  the  expansion  curves.  It 
is  most  frequently  taken  from  the  end  of  the  stroke,  the  pressure  being  ascertained  by  continuing  the 
curve  h  k  to  the  line  Uxu.  Putting  W=  calculated  water  evaporated  per  hour,  u  =  weight  per  cubic 
foot  of  steam  due  to  the  total  pressure  at  end  of  stroke,  v  =  the  corresponding  weight  per  cubic  foot 
of  cushioned  steam,  and  c  =  proportion  of  cylinder  capacity  represented  by  clearance  spaces,  and 
using  also  part  of  the  Bymbols  previously  named,  we  have 

11' =  [(1  +  c)u  —  cv]  x    '-x2SxJ?x  60  =  .8333  A  Sit  [(I  +  c)u-cv]. 
1  1 1 

Except  in  rare  instances  when  using  superheated  steam,  the  calculated  weight  of  steam  is  less  than 
the  actual  amount,  on  account  of  c\  Under  condensation.  This  condensation  increases  rapidly  with  the 
degree  of  expansion.     Ordinarily  90  per  cent,  or  more  of  the  feed-water  or  water  actually  evaporated 

will  be  accounted  for  by  the  indicator  when  the  steam  follows  about  seven-eighths  of  the  stroke;  and 



in  many  cases  only  about  one-half  of  the  actual  quantity  will  be  thus  accounted  for  by  the  indicator 
when  the  steam  is  expanded  ten  times.  The  discrepancy  varies  with  the  quality  of  the  steam,  and  all 
the  thermal  conditions  under  which  the  work  is  performed. 

The  indicator  diagrams  from  non-condensing  engines,  Figs.  2.';(.I9  to  2402,  are  reduced  from  a  "  Trea- 
tiseonthe  Steam-Engine  Indicator,"  by  Mr.  Charles  T.  Porter,  revised  by  Mr.  F.  W.  Bacon.  Figs.  2399, 
2-Hmi,  and  2-ln]  arc  from  locomotives.  Fig.  2399  is  as  near  a  full-stroke  diagram  as  can  be  obtained 
with  a  slide-valve.     It  differs  however  from  full-stroke  diagrams  usually  obtained,  from  the  fact  that 

tire  steam-pressure  at  the  beginning  of  the  stroke  is  less  than  near  the  end,  showing  that  the  steam 
could  not  enter  with  sufficient  rapidity  to  both  reheat  the  cylinder  and  keep  up  the  pressure.  The 
diagram  shown  in  Fig.  2400  was  taken  from  a  locomotive  on  the  Philadelphia,  Wilmington,  and  Bal- 
timore Railroad,  at  a  speed  of  more  than  60  miles  per  hour,  with  the  engine  making  more  than  300 
revolutions  per  minute  ;  under  which  circumstances  it  must  be  considered  a  remarkably  good  diagram. 
The  early  release  is  necessary  at  such  high  speeds,  to  free  the  cylinder  and  permit  the  cushion  to  act 
efficiently  before  the  return  stroke.     The  high  back  pressure  is  necessary  to  secure  draught  with  the 

blast-pipes.  The  diagram  shown  in  Fig.  2401  was  taken  from  an  English  locomotive  with  revers- 
ing lever  in  the  first  notch,  and  shows  the  general  shape  of  diagrams  taken  from  engines  cutting  off 
short  with  a  lap-valve,  extreme  cushioning  being  a  prominent  feature.  The  diagram  shown  in  Fig. 
2402  was  taken  from  an  engine  with  disengaging  cut-off.  The  loops  below  the  atmospheric  line 
represent  resistances  against  the  piston,  and  show  the  common  defect  that  the  engine  was  insufficient- 
ly loaded  to  secure  economy.     The  proper  remedy  is  to  provide  more  work  for  the  engine,  which  will 



be  accomplished  without  extra  cost  for  fuel.  The  diagrams  shown  in  Fig.  2403  were  taken  from  one 
of  the  vertical  cylinders  of  the  United  States  Coast  Survey  steamer  Bache,  at  a  speed  too  slow  for 
economy.  Water  collected  above  the  piston  in  such  quantities  as  to  cause  the  pressures  at  the 
latter  part  of  the  stroke  to  rise  above  the  theoretical  curve  in  the  manner  shown.  Fig.  2-404  repre- 
sents an  average  diagram  taken  from  the  single  vertical  engine  of  the  United  States  Revenue  steamer 
Gallatin ;  and  Figs.  2405  and  2406  represent  average  diagrams  from  the  high-  and  low-pressure  cylin- 
ders respectively  of  the  compound  engine  of  the  United  States  Revenue  steamer  Rush.* 

Indicator  diagrams  are  occasionally  taken  with  the  drum  operated  by  connection  to  other  parts  of 
the  engine  than  the  main  piston ;  for  instance,  to  the  cross-head  of  the  slide-valve,  or  by  a  cord  to 
cause  the  same  to  revolve  coincidently  with  the  main  shaft.  Such  diagrams  are  instructive  to  show 
the  relative  times  occupied  by  the  admission  and  release  of  the  steam,  which  are  not  shown  on  an 

ordinary  diagram  on  account  of  the  slow  motion 



of  the  paper  near  the  end  of  the  stroke.  They 
are  not,  however,  considered  of  great  practical 
utility,  and  are  obtained  chiefly  as  exercises, 
puzzles,  and  curiosities.  Indicator  diagrams 
have  been  taken  on  a  disk  rotated  back  and 
forth  by  the  engine,  the  measurements  being 
made  on  radial  ordinates. 

AfcNaughVs  Indicator. — Fig.  2407  is  a  ver- 
tical section,  Fig.  240S  a  vertical  elevation,  Fig. 
2409  a  horizontal  section,  and  Fig.  2410  a  plan 
of  this  instrument.  This  is  the  general  form  of 
indicator  exclusively  in  use  previous  to  the  year 
1862.  The  principal  features  will  be  understood 
from  the  general  description  in  connection  with 
Fig.  2388.  The  paper  is  wound  upon  the  drum 
E,  and  held  in  place  by  a  double  clip-spring  I. 
The  drum  E  is  set  on  an  interior  cylinder  E,  and 
a  slot  in  the  bottom  of  the  former  engages  with 
a  pin  in  the  latter.  The  cylinder  and  drum  are 
revolved  together  through  a  portion  of  a  revo- 


lution  in  one  direction  by  a  cord  secured  at  one  end  in  a  groove  or  cylinder  E,  and  led  over  one  or 
more  guide-pulleys/  to  levers  or  equivalents  operated  by  the  main  piston.  The  cylinder  E  is  retracted 
by  a  coiled  spring  shown  at  the  top  of  the  bearing  in  Fig.  2407.  The  piston-rod  b  of  the  indicator- 
piston  a  carries  near  its  middle  a  boss  to  which  the  free  end  of  the  spring  is  secured,  and  in  which 
is  a  mortise  to  receive  the  shank  of  a  pencil  carried  by  e,  which  is  hinged,  as  shown  plainly  in  Fig. 
2410,  so  that  the  pencil  may  be  turned  down  upon  the  paper  on  the  drum  or  thrown  back  from  the 
same.  A  spring  at  the  joint  of  the  pencil-holder  like  that  in  a  knife-handle  causes  the  pencil  to 
bear  lightly  upon  the  paper,  or  holds  it  back  when  removed. 

*  See  discussion  of  the  trials  of  revenue  steamers  bv  Mr.  C.  E.  Emerv,  in  the  (London)  Engineering,  and  in  the 
Journal  of  the  Franklin  Institute,  February,  1875.  See  also  Engineering,  vol.  xxi.,  and  Journal  of  the  Franklin 
Institute,  February,  1S76. 




At  high  speeds  the  weight  of  the  reciprocating  parts  of  the  McNaught  indicator  prevents  the  piston 
from  following  promptly  the  changes  of  pressure ;  and  the  sudden  admission  and  release  of  the  steam 
induce  vibration  in  the  spring  and  undulations  in  all  the  lines  and  curves  of  the  diagram,  of  such 
extent  that  the  distribution  of  the  steam  is  not  shown  satisfactorily;  and  the  period  of  vibration 
bein"-  rarely  a  factor  of  the  period  in  which  the  stroke  is  performed,  the  area  of  the  diagram  also 
becomes  incorrect,  so  that  the  power  cannot  be  accurately  ascertained.  The  first  attempt  to  reinedy 
this  difficulty  was  made  in  the  Gooch  indicator  for  use  on  locomotives,  in  which  the  motion  of  the 
pencil  compared  with  that  of  the  piston  was  multiplied  by  a  lever.  This  enabled  a  stiffer  spring  to 
be  used  for  the  same  scale  or  diagram,  and  the  momentum  of  the  parts  was  so  reduced  that  smooth 
diagrams  were  obtained  at  the  highest  speeds.  The  objection  was  that  the  pencil  moved  in  the  arc 
of  a  circle,  which  distorted  the  diagram  and  caused  difficulties  in  measuring  it  correctly. 

The  Richards  Indicator. — The  indicator  now  in  general  use  was  invented  by  Mr.  Charles  B.  Rich- 
ards  of  Hartford,  Conn.  It  was  first  brought  prominently  to  public  notice  at  the  International  Exhi- 
bition of  1862  in  London.  An  exterior  view  of  the  instrument  is  shown  in  Fig.  2411,  and  a  sec- 
tional view  of  the  cylinder  in  Fig.  2112.  The  piston  has  only  one-fourth  of  the  movement  of  the 
pencil,  and  connects  to  the  latter  through  a  simple  parallel  motion,  as  clearly  shown  in  the  drawing. 
This  instrument  gives  accurate  indications  at  either  slow  or  high  speeds.  There  are  no  undulations 
on  the  diagrams  except  at  high  speeds,  in  which  ease  they  are  limited  in  extent  and  confined  to  the 
early  part  of  the  stroke.  In  the  McNaught  indicator  there  was  difficulty  in  applying  the  pencil  to 
the  paper  when  the  former  was  in  motion.  In  the  Richards  instrument  the  parallel-motion  levers 
arc  secured  to  the  curved  arms  A' attached  to  a  sleeve  turning  on  the  case  of  the  instrument,  so  that 
the  pencil  ./,  carried  by  the  link  connecting  the  levers,  may  be  moved  freely  to  and  from  the  paper 
on  the  drum  A  A,  without  handling  the  parts  in  motion. 

The  Thompson  Indicator. — This  instrument,  illustrated  in  Fig.  2413,  was  patented  by  Mr.  J.  W. 
mmpson  in  the  year  1875.     It  is  a  modified  form  of  the  Richards  or  parallel-motion  indicator,  in 

which  a  simpler  form  of  parallel  mo- 
2413.  tioi)  is  used   than  that  applied  by  Mr. 

Richards,  whereby  the  mass  in  mo- 
tion is  still  further  reduced,  making 
it  somewhat  better  adapted  for  cx- 
tremelj  high  speeds.  The  lever  car- 
rying the  pencil  is  moved  to  and  from 
tiir  paper-drum  by  operating  the  han- 
dle attached  to  the  arm  as  shown,  and 
thus  partially  revolving  the  sleeve  A' 
on  the  upper  part  of  the  cylinder. 
The  construction  will  be  understood 
by  examining  the  drawing  in  connec- 
tion with  the  descriptions  of  the  other 

Application  ani>  Use  of  the  Indi- 
cator.— The  cocks  furnished  with  an 
indicator  are  usually  provided  with 
screw-threads  to  connect  with  the  fit- 
tings of  half-inch  iron  pipe  ;  and,  for 
short  connections,  pipes  of  that  size 
are  run  from  the  clearance  spaces  in 
the  cylinders  in  such  manner  as  to 
bring  the  indicator  into  an  erect  posi- 
tion. The  connection  should  not  be 
made  in  the  cylinder  passages  where 
a  current  will  pass  the  openings,  nor 
should  the  opening  be  placed  so  that 
the  piston  will  run  over  it.  Both  ends 
of  the  cylinder  should  be  indicated 
either  by  the  use  of  separate  instru- 
ments, by  shifting  the  instrument  from 
one  to  the  other,  or  by  bringing  the 
pipes  together  to  a  central  T-piece  to 
receive  the  instrument,  with  separate 
valves  for  each  of  the  branches.  When 
the  pipes  are  more  than  one  foot  in 
length,  they  should  be  larger  than  half-inch  ;  stop-valves  should  be  provided  in  each  branch  near  the 
cylinder,  and  a  three-way  cock  at  the  junction.  When  a  three-way  cock  is  not  used,  the  stop-cocks 
should  be  close  to  the  T-piece,  so  that  the  double  length  of  piece  will  not  be  filled  at  each  stroke. 
In  all  cases  the  pipes  should  be  felted,  as  otherwise  there  will  be  trouble  with  water  in  the  indicator- 
cylinder,  and  the  diagrams  will  rarely  be  accurate. 

"  The  motion  is  conveyed  from  the  main  piston  to  an  indicator-drum  in  various  ways.  In  condens- 
ing engines  the  cord  is  often  attached  directly  to  the  air-pump  levers.  Engine-beams  and  parallel- 
motion  levers  often  offer  similar  facilities.  For  large  engines,  used  on  sea  and  land,  permanent 
levers  are  erected  and  kept  in  motion ;  a  pin  on  a  lever  or  a  hook  on  the  end  of  a  sliding  rod  being 
arranged  near  the  instrument  for  the  attachment  of  the  hook  on  the  indicator-cord  at  any  time.  For 
the  temporary  application  of  the  indicator,  and  on  oscillating  cylinders,  a  reducing  wheel  is  used, 



similar  to  that  shown  in  Fig.  2414.  A  cord  is  attached  to  the  engine  cross-head  and  led  back,  paral- 
lel with  the  piston-rod  (over  a  leading  pulley  when  necessary),  to  the  larger  diameter  of  the  wheel, 
the  string  being  kept  tight  and  the  wheel  retracted  by  a  coiled  spring  inside  the  latter  ;  and  from  a 
small  wheel  on  the  side  of  the  larger  one  a  string  is  led  to  the  indicator.  Kings  of  different  sizes 
are  sometimes  provided  to  vary  the  size  of  the  small  wheel,  to  adapt  the  instrument  to  engines 
having  different  lengths  of  stroke. 

To  obtain  the  motion  from  the  piston  of  a  horizontal  engine,  it  is  customary  to  suspend  a  wooden 
lever  from  the  ceiling,  and  connect  it  by  a  slot  at  the  bottom  with  a  bolt  in  the  engine  cross-head,  as 


shown  in  Fig.  2415.  A  link  connection  may  be  used  instead  of  a  slot  and  pin.  The  whole  apparatus 
can  be  satisfactorily  constructed  with  soft-wood  boards  and  blocks  and  large  wood-screws.  The 
broad  surface  of  the  board  at  the  top  steadies  the  lever,  and  the  smooth  shank  of  the  screw  makes  a 
good  bearing.  The  link  may  be  connected  to  the  lever  by  a  wood-screw  at  the  bottom ;  and  if  there 
is  no  satisfactory  attachment  to  the  cross-head,  a  block  can  be  clamped  on  with  wood-screws,  and  a 
screw  inserted  in  the  side  of  the  same  as  a  bearing  for  the  link.  The  cord  to  the  indicator  may  be 
run  horizontally  from  a  point  in  the  fulcrum  and  over  a  pulley  to  the  indicator,  as  shown,  or  a  block 
secured  to  the  side  of  the  lever,  and  a  cord  run  diagonally  to  the  instrument,  as  represented  by  the 
detached  view  in  Fig.  2415.  Care  should  be  taken  that  the  average  direction  assumed  by  the  cord  be 
at  right  angles  to  the  middle  position  of  the  lever-arm  operating  it ;  that  is,  the  cord  should  be  at 
right  angles  to  the  line  A  B  in  Fig.  2415.  Often  the  lever  is  run  horizontally  to  the  wall  or  a 
trestle.  Fine  wire  is  sometimes  used  instead  of  cord,  to  reduce  the  stretch ;  and  it  will  often  be 
advantageous  to  use  wire  for  the  direct  portions  and  cord  at  the  pulleys.  Hooks  are  provided  to 
disconnect  the  cord  near  the  instrument. 

Fig.  2416  shows  in  plan  a  detent  sometimes  applied  to  the  Richards  indicator.  "When  the  arms 
carrying  the  pencil  are  thrown  back  as  shown,  a  small  pawl  G  is  released,  and,  catching  into  teeth  on 
the  bottom  of  the  paper-drum  cylinder,  holds  it  in  the  extreme  position  to  which  it  is  drawn  by  the 
cord.  Upon  moving  the  pencil  toward  the  drum,  a  cam  on  the  sleeve  of  the  arm  presses  back  the 
pawl,  thus  permitting  the  drum  to  continue  its  motion.  By  releasing  the  pawl  as  the  cord  tightens, 
the  drum  is  put  in  operation  without  jar.  This  figure  shows  also  the  metallic  pencil  furnished  by 
Messrs.  Elliot  Brothers  with  the  Richards  indicator,  for  use  in  connection  with  prepared  paper. 

In  using  an  indicator,  the  pipes  should  be  heated  if  possible  before  turning  steam  on  the  instru- 
ment, and  the  piston  should  be  permitted  to  work  up  and  down 
for  a  time  before  applying  the  pencil  to  the  paper.  The  atmos- 
pheric line  should  not  be  taken  until  after  the  diagram,  so  as 
to  be  sure  that  the  whole  instrument  is  thoroughly  heated.  The 
atmospheric  line  will  be  below  its  true  position  if  taken  before 
the  indicator  spring  is  heated.  The  speed  of  the  engine  while 
the  indicator  is  in  use  should  be  accurately  ascertained.  If  a 
counter  is  attached,  it  is  better  to  note  its  reading  before  taking 
the  diagram,  and  again  afterward ;  or  the  revolutions  may  be 
counted  while  inspecting  the  second-hand  of  a  watch.  If  the 
count  be  commenced  on  the  even  minute,  the  last  number  counted 
before  the  minute  expires  is  the  correct  one.  The  steam-pres- 
sure, vacuum,  and  other  customary  data  should  also  be  noted  on 
the  diagram  in  connection  with  the  date  and  hour. 

MoritCs  Continuous  Indicator. — This  is  an  early  example  of  a 
class  of  devices  designed  to  obtain  a  record  of  the  pressure  in  a 
steam-cylinder  for  a  considerable  length  of  time.  Fig.  2417  is 
a  side  elevation,  Fig.  2418  an  end  elevation,  and  Fig.  24d9  a  plan 

of  the  apparatus.  G-  is  a  cock  in  a  pipe  connecting  with  the  steam-cylinder.  H  is  the  indicator- 
cylinder  arranged  horizontally,  in  which  a  solid  piston  is  accurately  fitted  to  work  steam-tight.  Near 
the  middle  of  the  piston-rod  m,  which  is  properly  guided  in  a  rectilinear  course,  is  inserted  the  lower 
end  of  a  long  parabolic  spring  re,  the  other  extremity  of  which  is  fixed  to  the  summit  of  a  standard 
/,  forming  part  of  the  framework  of  the  machine,  the  spring  being  so  fitted  as  to  admit  a  certain 




amount  of  travel  of  the  piston  in  both  directions.  The  piston-rod  carries  also  a  small  pencil  o,  for 
the  purpose  of  tracing  the  different  degrees  of  tension  of  the  steam  on  the  opening  of  the  lower 
cock  67.     Two  pencils  pp  are  placed  in  holders  fixed  to  the  framing  exactly  opposite  to  the  point  at 

which  the  pencil  o  stands  when  the  stop-cock  G  is  shut,  to  mark 
a  continuous  atmospheric  line.  A  third  pencil  g,  which  is  sus- 
ceptible of  a  slight  degree  of  vertical  motion  in  its  socket,  and 
is  destined  to  mark  the  termination  of  each  stroke,  is  brought 
into  contact  with  the  paper  by  placing  the  instrument  so  that 
the  working-beam,  cross-head,  or  any  other  rigid  part  of  the 
engine  may  touch  lightly  at  the  end  of  the  stroke  the  top  of 
an  upright  rod  u,  which  is  connected  by  a  system  of  levers  rst 
with  the  top  of  the  pencil  q.  A  continuous  band  or  roll  of 
paper  maybe  subjected  to  the  action  of  this  machine  for  an 
indefinite  period,  so  as  to  produce  diagrams  representing  the 
action  of  the  engine  during  successive  strokes.  The  roll  of 
paper  is  first  wound  upon  the  cylinder  Z,  by  means  of  the  han- 
dle y  ;  it  is  then  passed  over  the  three  small  rollers  vvv  placed 
to  oppose  the  pressure  of  the  pencils,  and  is  received  upon  the 
cylinder  J/  situated  at  the  opposite  end  of  the  framing  Q  Q. 
The  axis  of  this  latter  cylinder  is  produced  on  one  side  so  as  to 
form  also  the  axis  of  a  conical  pulley  or  fusee  N,  opposite  to 
which  is  situated  a  cylindrical  drum  O,  which  receives  a  uni- 
form motion  from  any  rotating  part  of  the  engine  to  be  oper- 
ated on,  by  means  of  a  worm-wheel  w  on  its  a.\is,  gearing  with 
an  endless  screw  on  the  axis  of  the  pulley  P.  The  cylindrical 
roller  0  communicates  motion  to  the  conical  roller  N  by  a  cord 
wrapped  round  both,  and  fastened  at 
opposite  extremities  of  each.  The 
object  of  this  arrangement  is  to  com- 
pensate for  the  increased  surface  ve- 
il h  it  \  due  to  the  increased  diameter 
of  the  cylinder  M  as  the  paper  is 
wound  on  to  it,  by  imparting  to  it  a 
proportionally  retarded  motion. 
The  method  provided  in  the  above 
apparatus  for  operating  the  band  of  paper  from  a  rotating  part  of  the  engine  will  not  give  accurate 
results,  as  the  pressures  in  the  cylinder  do  not  represent  the  rotative  efforts  on  the  crank-pin.  The 
paper  should  be  propelled  in  a  series  of  steps,  so  to  speak,  by  a  motion  derived  from  that  of  the 

main  piston,  as  has  been  done  in  other 
apparatus  for  a  similar  purpose. 

Addon  and  Storm's  SU ma-Power  Me- 
ter or  Continuous  Indicator. — A  section 
through  the  case  of  this  instrument  is 
shown  in  Tig.  2420.  A  is  the  indicator- 
cylinder,  the  ends  of  which  are  connect- 
ed to  the  ends  of  the  cylinder  of  the  en- 
gine through  pipes  in  continuation  of  a 
and  b.  The  indicator-piston  is  double- 
acting,  and  is  controlled  by  a  spring  E 
in  the  usual  way.  The  piston-rod  car- 
ries up  and  down  with  it  an  integrating 
disk  I),  with  an  attached  long  pinion  By 
the  disk  and  pinion  being  free  to  revolve 
on  the  rod  between  the  collars  shown. 
F  is  a  motion-disk,  adjusted  in  its  bear- 
ings to  press  lightly  against  the  inte- 
grating disk  D.  A  rotary  motion  alter- 
nately in  opposite  directions  is  given  to 
disk  F  by  a  connection  to  the  main  pis- 
ton. When  the  cocks  in  connections  are 
shut  and  the  atmosphere  admitted  to 
both  sides  of  the  indicator- 
piston,  the  integrating  disk 
D  bears  at  the  centre  of  the 
disk  F,  and  receives  no  mo- 
tion therefrom.  When  the 
connections  are  opened,  the 
indicator  -  piston  will  move 
upward,  when  the  excess  of 
pressure  is  on  the  bottom, 
carrying  up  the  disk  B,  which  will  receive  motion  from  the  disk  F  proportioned  to  the  distance  it  is 
moved  above  the  centre  of  the  latter.  When  the  excess  of  pressure  is  on  the  top  of  the  indicator- 
piston,  the  disk  D  is  carried  below  the  centre  of  the  disk  F,  and  at  that  time  the  direction  of  the 



main  piston  will  have  been  reversed ;  so  the  movement  of  the  disk  F  will  also  be  reversed,  and  the 
disk  _D  receive  motion  proportioned  as  before  to  its  distance  from  the  centre  of  F,  but  in  the  same 
direction  as  before.  The  motion  of  the  disk  D  is  imparted  through  the  long  pinion  B  to  a  toothed 
wheel  C,  which  operates  the  indices  of  a  recording  apparatus  not  shown.  The  principles  of  the 
operation  of  integrating  apparatus  of  this  character  are  explained  in  the  article  Dynamometers. 

A  very  accurate  estimate  of  the  average  power  developed  by  marine  engines  may  be  obtained  by 
fixing  the  cut-off,  taking  indicator  diagrams  at  intervals  with  different  steam-pressures,  ascertaining 
accurately  the  average  steam-pressures  by  diagrams  from  a  recording  gauge  (see  Gauges,  Steam),  or 
by  frequent  observations  of  a  common  gauge,  then  calculating  the  average  relation  between  the 
initial  and  mean  pressures  of  the  diagrams,  and  applying  the  same  ratio  to  find  the  average  mean 
pressure  from  the  average  steam-pressure. 

Speed-Indicators. — Two  types  of  apparatus  are  available  to  indicate  speed.  In  the  first  type  an 
index  shows  on  a  scale  the  speed  at  the  time,  and  varies  its  position  with  the  velocity.  This  is 
readily  accomplished  by  connecting  the  index  with  the  slide  of  an  ordinary  conical  pendulum  or 
governor  for  stationary  machinery,  and  with  any  of  the  forms  of  marine  governor  when  applied  to  a 
vehicle.  A  common  high-speed  centrifugal  governor,  acting  against  the  resistance  of  springs,  is  quite 
sufficient  when  care  is  taken  to  proportion  the  springs  so  that  the  balls  and  slide  will  take  different 
positions  at  different  speeds.  Apparently  overlooking  this  simple  arrangement,  prominent  manu- 
facturers have  used  a  governor  to  operate  a  valve  regulating  a  supply  of  water  under  pressure  to  an 
ordinary  pressure-gauge,  which  thereby  indicated  changes  of  speed,  but  in  a  ratio  different  from  the 
actual  changes,  which  would  not  have  been  the  case  had  the  governor-slide  been  attached  directly  to 
the  index  and  the  remainder  of  the  apparatus  omitted.  Speed-indicators  have  also  been  made  with 
bent  glass  tubes,  in  which  the  level  of  the  mercury  was  varied  by  centrifugal  force. 

In  other  apparatus  a  similar  result  is  accomplished  in  a  complex  manner  by  differential  mechan- 
ism, in  which  the  difference  between  the  speeds  of  the  machine  tested  and  of  a  timepiece  varied  the 
position  of  an  index  on  the  scale. 

The  second  type  of  apparatus  is  based  somewhat  on  the  principle  of  the  chronograph.  A  belt  of 
paper  is  connected  to  move  at  a  rate  proportioned  to  that  of  the  vehicle  or  machine,  and  marks  are 
made  on  the  same  at  regular  intervals  by  electrical  or  mechanical  connection  with  a  timepiece,  the 
distances  between  the  dots  representing  the  velocities  during  that  period. 

Wythe's  Recording  Speed-Indicator  is  designed  to  record  the  speed  of  trains  on  railroads.  A  band 
of  paper  on  a  drum  is  propelled  by  gearing  connected  with  the  axle  of  a  car,  and  a  pencil  is  traversed 
longitudinally  of  the  cylinder  once  an  hour  by  clockwork.  A  stop  of  the  train  therefore  is  indicated 
by  a  line  parallel  with  the  axis,  and  for  varying  speeds  the  inclinations  of  the  lines  vary.  The  strip 
of  paper  is  ruled  with  longitudinal  lines  representing  minutes  of  time,  and  with  transverse  lines 
representing  distance — that  is,  miles  or  quarter  miles.  The  paper  has  also  printed  on  it  the  names 
of  the  stations  at  such  distances  as  they  occur  according  to  the  scale.  In  some  cases  the  grades  and 
curves  are  also  printed  on  the  slip.  C.  E.  E. 

INDUCTION  COIL.     Sec  Electric  Machines  (Static). 

INERTIA.     See  Dynamics. 

INJECTORS.  An  injector  is  an  instrument  used  principally  for  forcing  water  into  a  boiler.  By 
its  agency,  a  gas  issuing  from  a  reservoir  under  a  high  pressure  not  only  acquires  velocity  enough  to 
carry  it  back  again  through  another  opening  into  the  same  reservoir,  but  it  also  transports  back 
with  it  several  times  its  weight  of  water.  When  it  is  considered  that  the  steam  which  leaves  the 
boiler  under  a  high  pressure  with  great  velocity  is  condensed  en  route,  and  reenters  the  boiler  as 



water  at  a  greatly  reduced  volume,  the  principles  which  govern  the  machine  appear  clear.  Thus,  if 
an  opening  one  inch  in  area  be  made  in  a  boiler  carrying  15  lbs.  pressure  above  the  atmosphere  (30 
lbs.  above  zero),  if  there  is  no  reduction  by  friction,  the  steam  will  issue  from  it  with  a  velocity  of 
approximately  1,440  feet  a  second ;  and  the  steam  which  would  issue  from  this  opening  would  be  10 
cubic  feet  in  a  second,  which  would  weigh  two-thirds  of  a  pound.  When  this  steam  is  condensed  to 
water,  it  maintains  its  velocity,  but  is  reduced  in  volume  from  10  cubic  feet  to  g\j  of  a  cubic  foot ; 
or  in  other  words,  the  stream  of  steam  of  one  inch  area,  which  issued  from  the  boiler  with  a  velocity 
of  1,440  feet  a  second,  would  be  reduced  to  a  stream  of  water  fa  of  an  inch  in  diameter,  having  the 
same  velocity,  1,440  feet  per  second.  The  laws  of  hydraulics  show  that  water  will  issue  from  a  ves- 
sel under  a  pressure  of  15  lbs.  per  square  inch  with  a  velocity  of  45  feet  per  second,  and  that  any 
stream  having  a  greater  velocity  than  45  feet,  if  directed  against  an  orifice  in  the  vessel,  would  enter 
the  vessel  notwithstanding  the  pressure  of  15  lbs.  in  the  vessel.  The  jet  of  condensed  steam  has  a 
velocity  of  1,440  feet,  or  more  than  30  times  that  necessary  to  reenter  the  boiler.  Its  velocity  may 
be  reduced  by  allowing  it  to  mix  with  nearly  900  times  its  weight  of  water,  and  the  mixture  will  stiil 
retain  the  velocity  necessary  to  reenter  the  boiler.  In  the  case  of  the  injector,  the  same  water  which 
serves  to  condense  the  steam  mingles  with  it  and  enters  the  boiler  as  the  feed.  These  figures  are 
reduced  in  practice  by  the  friction  of  the  sides  of  the  orifices.  The  amount  of  water  in  excess  which 
the  steam  can  carry  back  is  very  much  less  than  900  times  its  weight  in  practice.  This  arises  mainly 
from  the  friction  of  the  jets.  The  friction  of  the  sides  of  the  discharge  orifice  reduces  the  velocity  of 
the  issuing  stream  to  six-tenths  of  the  theoretical  velocity,  and  that  of  the  receiving  orifice  to  six- 
tenths  of  the  remainder,  making  a  total  reduction  to  nearly  one-third  of  the  original,  or  about  5n0 
feet  a  second,  the  friction  of  the  pipes  and  bends  reducing  it  still  more.  In  practice,  therefore, 
tlie  velocity  of  the  issuing  steam  would  be  900,  and  of  the  entering  stream  would  need  to  be  70  feet 
per  second.  The  relative  amounts  of  steam  and  water  then  become  as  9002 -r- 702  =  100.  The 
steam  then  may  mingle  with  160  times  its  weight  of  water,  raising  its  temperature  from  100°  to 
109°,  and  still  retain  velocity  enough  to  force  the  mixture  back  into  the  boiler.  If  the  supply  of 
water  is  reduced,  the  entering  stream  becomes  hotter  and  hotter,  until  a  temperature  is  readied  at 
which  all  of  the  steam  is  not  condensed  ;  at  this  point  the  injector  ceases  to  work.  The  final  tem- 
perature of  the  mixture  of  steam  and  water,  at  which  some  of  the  steam  escapes  without  being  con- 
densed, is  much  less  than  212  . 

The  general  features  which  may  be  found  in  all  varieties  of  injectors  are  represented  in  Fig. 
2421,  which  is  thus  explained  :  "It  consists  of  a  pipe  .1  fur  the  admission  of  steam,  which,  escaping 

through  the  nozzle  C  at  a  high  ve- 
9421,  locity,  is  joined    by  water,  which, 

flowing  in  through  the  pipe  B,  and 
passing  around  the  end  of  the  noz- 
zle C,  mingles  with  and  conden-es 
t!n-  -team  in  the  conical  pipe  ]>, 
and  is  driven  through  the  pipe  // 
and  check-valve  /  into  the  boiler; 
of  steam  or  water,  from 
want  of  adjustment,  escaping  by 
the  outlet  E  /■'  and  pipe  G.  The 
[nuts  Bhown  arc  common  to  all  forms  of  injectors,  under  various  shapes  and  modifications,  and  have 
been  named — C,  receiving-tube:  I),  combining-tube ;  //,  delivery-tube;  /,  check-valve :  E  F,  over- 
flow; and  G,  overflow  nozzle.  During  the  passage  of  the  water  from  D  to  H,  it  is  driven  across  the 
space  F.  If  too  much  water  is  being  supplied  to  the  steam,  some  water  may  escape  at  this  point  and 
flow  out  through  the  overflow  nozzle  0  :  while  if  there  be  too  little  water,  air  will  be  drawn  in  at 
G  and  carried  into  the  boiler  with  the  water." 

The  chief  differences  between  the  various  injectors  in  the  market  consist  in  the  relative  proportions 
of  the  parts,  and  in  the  means  employed  for  changing  these  proportions,  cither  automatically  or  oth- 
erwise, so  as  to  adapt  the  instrument  to  variation  of  steam-  or  water-supply.  Many  injectors,  also, 
are  provided  with  lifting  attachments,  to  enable  them  to  raise  and  deliver  water  from  lower  levels. 

A  series  of  injector  trials,  probably  the  most  important  and  extended  ever  made,  were  conducted 
in  May,  1879,  by  Park  Benjamin's  Scientific  Expert  Office  of  New  York,  with  the  object  of  obtaining 
new  and  reliable  data  regarding  the  performances  of  these  machines  expressly  for  the  present  work. 
Tests  were  made  of  three  forms  of  Sellers  injectors  and  of  the  Hancock  inspirators,  these  instru- 
ments having  already  given  notably  good  results  under  conditions  of  actual  use.  Reports  of  both 
series  of  trials  are  given  in  full  below.  The  experiments  were  undertaken  with  a  view  to  sub- 
mitting the  injectors  to  the  most  thorough  trials  that  could  be  devised,  in  order  to  cover  all  condi- 
tions occurring  in  practice. 

The  Sellers  Injectors. — Report  of  Tests  conducted  by  Park  Benjamin's  Scientific  Expert  Office, 
May,  1879,  at  the  Works  of  Messrs.  W.  Sellers  d>  Co.,  Philadelphia.  Trials  in  charge  of  Richard 
H.  'Bud,  C.  E. 

Preparations  and  Conditions. — The  supply-water  for  the  injectors  was  delivered  through  a  pipe 
in  such  a  manner  that  it  could  be  run  into  a  tank  elevated  above  the  level  of  the  injector  into  a  tank 
below  this  level,  or  could  be  admitted  directly  to  the  injector  under  the  pressure  in  the  main,  as 
desired.  It  could  also  be  drawn  directly  from  the  pipe  or  through  a  Wbrthington  water-meter. 
Both  the  supply  and  delivery  pipes  connected  with  the  injector  were  provided  with  cups  through 
which  water  was  allowed  to  escape  from  these  pipes,  and  in  which  a  thermometer  could  be  placed 
for  the  purpose  of  ascertaining  the  temperature  of  the  feed  and  delivery  water.  The  steam-supply 
pipe  leading  to  the  injector  was  provided  with  a  throttle-valve,  for  the  purpose  of  reducing  the 



steam-pressure  when  desired;  and  a  sensitive  pressure-gauge  was  connected  to  the  steam-pipe 
between  the  throttle-valve  and  the  injector.  This  same  pressure-gauge  could  be  connected  with 
the  delivery-pipe  between  the  injector  and  the  check-valve  of  the  boiler,  so  that  it  could  be  used 
to  indicate  the  water-pressure  by  closing  the  valve  in  the  pipe  connecting  the  gauge  with  the 
steam-pipe,  and  opening  the  valve  in  the  pipe  connecting  the  gauge  with  the  delivery-pipe.  The 
delivery-pipe  was  connected  directly  with  the  feed-pipe  of  the  boiler  that  supplied  steam  to  the 
injector,  and  there  was  a  safety-valve  in  the  delivery-pipe  (which  could  be  loaded  to  any  desired 
pressure)  between  the  injector  and  the  check-valve  of  the  boiler.  A  large  Harrison  boiler,  having 
48  square  feet  of  grate-surface,  and  consisting  of  1,088  cast-iron  spheres,  each  8  inches  in  diameter, 
was  used  to  furnish  steam  for  the  experiments.  The  boiler  was  managed  by  an  exceptionally  expert 
fireman,  who  maintained  the  steam-pressure  at  any  point  required  without  sensible  variation.  ^  The 
water-supply  pipes  were  so  arranged  that  by  heating  water  in  the  elevated  tank  previously  mentioned 
(which  could  be  done  by  blowing  live  steam  into  the  tank,  or  feeding  hot  water  into  the  tank  by  the 
injector),  cold  water  could  be  mixed  with  this  in  any  desired  proportion,  in  the  pipe  connecting  the 
tank  with  the  supply-pipe  of  the  injector,  so  that  the  highest  temperature  of  feed-water  admissible 
could  readily  be  determined. 

A  scaffolding  was  constructed  on  the  roof  of  the  testing-room,  and  steam,  supply,  and  delivery 
pipes  were  provided,  for  connecting  the  injector  at  a  considerable  elevation  above  a  portable  tank  in 
the  testing-room,  for  experiments  with  lifts  greater  than  could  be  measured  when  the  injector  was 
used  on  the  lower  level.  The  supply-pipe  for  high  lifts  was  made  in  sections,  so  that  the  lift  could  be 
readily  varied.  A  sensitive  chemical  thermometer  was  used  for  measuring  temperatures,  and  this 
was  tested  by  being  placed  in  boiling  water  and  in  melting  ice,  and  found  correct  at  these  two  points. 
The  water-meter  was  also  carefully  tested  by  running  water  through  it  at  various  rates  into  a  tank 
of  known  capacity.  It  was  found  that  the  readings  of  the  meter  were  somewhat  in  excess,  the  re- 
sults of  a  number  of  trials  at  various  rates  giving  an  actual  delivery  of  45.4  cubic  feet  for  a  delivery 
as  indicated  by  meter  of  46.3  cubic  feet ;  so  that  the  proper  correction  for  delivery  was  made  by 


multiplying  the  readings  of  the  meter,  in  every  instance,  by  —  —  =  0.981. 
f }    a  o  463 

The  Injectors. — Three  patterns  of  injectors  were  tried  in  these  experiments,  and  descriptions  of 
each,  with  results  obtained,  are  appended.  All  the  injectors  had  the  same  numerical  size,  No.  6,  the 
number  indicating  that  the  smallest  diameter  of  the  delivery  tube  was  6  millimetres  or  0.2362  inch. 
This  dimension  was  carefully  measured  in  the  case  of  each  injector. 

The  general  features  of  the  injectors  used  in  these  experiments  cover,  with  the  exception  of  special 
details  of  construction,  nearly  all  the  varieties  in  the  market ;  illustrating — 

1.  The  injector  with  automatic  adjustment  of  combining-tube  and  water-supply,  in  connection  with 
a  lifting  attachment ; 

2.  The  non-adjustable  injector  with  fixed  nozzles,  non-lifting  ; 

3.  The  non-adjustable  injector  with  fixed  nozzles,  in  connection  with  a  lifting  attachment. 

These  instruments  have,  however,  some  special  details  of  construction,  as  will  appear  by  the  de- 
scriptions that  follow. 

1.  The  Self-Adjusting  1876  Injector. — An  elevation  of  this  injector  is  shown  in  Fig.  2422,  and  a 
sectional  view  in  Fig.  2423.  The  injector  is  self-contained ;  or  in  other  words,  it  has  both  steam 
and  check  valves,  so  that  it  can  be  connected  directly  without  other  fittings,  although  of  course  it  is 



generally  desirable  to  place  another  stop-valve  in  the  steam-pipe,  and  a  check-valve  in  the  delivery- 
pipe,  so  that  the  injector  can  be  taken  to  pieces  or  disconnected  at  any  time.  Another  important 
feature  of  this  injector  is,  that  it  is  operated  by  a  single  handle,  and  that  the  waste-valve  is  only 
open  at  the  instant  of  starting. 

Referring  to  Fig.  2423,  A  is  the  receiving-tube,  which  can  be  closed  to  the  admission  of  steam 
by  the  valve  X.  A  hollow  spindle  passing  through  the  receiving-tube  into  the  combining-tube  is 
secured  to  the  rod  B,  and  the  valve  X  is  fitted  to  this  spindle  in  such  a  way  that  the  latter  can  be 
moved  a  slight  distance  (until  the  stop  shown  in  the  figure  engages  with  valve  X\  without  raising 
the  valve  X  from  its  seat.  A  second  valve  IT,  secured  to  the  rod  B,  has  its  seat  in  the  upper  side 
of  the  valve  X,  so  that  it  can  be  opened  (thus  admitting  steam  to  the  centre  of  the  spindle)  with- 

out raising  the  valve  X  from  its  seat,  if  the  rod  B  is  not  drawn  out  any  farther,  after  the  stop  on 
the  hollow  spindle  comes  in  contact  with  the  valve  X.  I)  is  the  delivery-tube,  0  an  overflow  open- 
ing into  space  C,  K  the  check-valve  in  delivery-pipe,  mid  I'  R  the  waste-valve.  The  upper  end  of 
the  combining-tube  has  a  piston  N N  attached  to  it,  capable  of  moving  freely  in  a  cylindrical  portion 
of  the  shell  MM,  and  the  lower  end  of  the  combining-tube  slides  in  a  cylindrical  guide  formed  in 
the  upper  end  of  the  delivery-tube. 

The  rod  B  is  connected  to  a  cross-head  which  is  fitted  over  the  guide-rod  ./,  and  a  lever  H  is  secured 
to  the  cross-head.  A  rod  L  attached  to  a  lever  on  the  top  end  of  the  screw  waste-valve  passes  through 
an  eye  that  is  secured  to  the  lever  II ;  and  stops  T,  Q  control  the  motion  of  this  rod,  so  that  the 
waste-valve  is  closed  when  the  lever  H  has  its  extreme  outward  throw,  and  is  opened  when  the  lever 
is  thrown  in  so  as  to  close  the  steam-valve  X,  while  the  lever  can  be  moved  between  the  positions  of 
the  stops  P,  Q  without  affecting  the  waste-valve.  A  latch  Via  thrown  into  action  with  teeth  cut  in 
the  upper  side  of  the  guide-rod  J,  when  the  lever  H  is  drawn  out  to  its  full  extent  and  then  moved 
back ;  and  this  click  is  raised  out  of  action  as  soon  as  it  has  been  moved  in  far  enough  to  pass  the 
last  tooth  on  the  rod  J.  An  air-vessel  is  arranged  in  the  body  of  the  instrument,  as  shown  in  the 
figure,  for  the  purpose  of  securing  a  continuous  jet  when  the  injector  and  its  connections  arc  exposed 
to  shocks,  especially  such  as  occur  in  the  use  of  the  instrument  on  locomotives. 

The  manipulation  required  to  start  the  injector  is  exceedingly  simple — much  more  so  in  practice, 
indeed,  than  it  can  be  rendered  in  description.  Moving  the  lever  H  until  contact  takes  place  between 
valve  A' and  stop  on  hollow  spindle,  which  can  be  felt  by  the  hand  upon  the  lever,  steam  is  admitted 
to  the  centre  of  the  spindle,  and,  expanding  as  it  passes  into  the  delivery-tube  D  and  waste-orifice  P, 
lifts  the  water  through  the  supply-pipe  into  the  combining-tube  around  the  hollow  spindle,  acting 
after  the  manner  of  an  ejector  or  steam-siphon.  As  soon  as  solid  water  issues  through  the  waste- 
orifice  P,  the  handle  77  may  be  drawn  out  to  its  full  extent,  opening  the  steam-valve  A' and  closing 
the  waste-valve,  when  the  action  of  the  injector  will  be  continuous  as  long  as  steam  and  water  are 
supplied  to  it. 

To  regulate  the  amount  of  water  delivered,  it  is  necessary  only  to  move  in  the  lever  H  until  the 
click  engages  any  of  the  teeth  on  the  rod  J,  thus  diminishing  the  steam-supply,  as  the  water-supply  is 
self-regulating.  If  too  much  water  is  delivered,  some  of  it  will  escape  through  0  into  C,  and,  pressing 
on  the  piston  NX,  will  move  the  combining-tube  away  from  the  delivery-tube,  thus  throttling  the 
water-supply;  and  if  sufficient  water  is  not  admitted,  a  partial  vacuum  will  be  formed  in  C,  and  the 
unbalanced  pressure  on  the  upper  side  of  the  piston  XX  will  move  the  combining-tube  toward  the 
delivery-tube,  thus  enlarging  the  orifice  for  the  admission  of  water.  From  this  it  is  evident  that  the 
injector,  once  started,  will  continue  to  work  without  any  further  adjustment,  delivering  all  its  water  to 



the  boiler,  the  waste-valve  being  kept  shut.  By  placing  the  hand  on  the  starting-lever,  it  is  easy  to 
tell  whether  or  not  the  injector  is  working ;  and  if  desired,  the  waste-valve  can  be  opened  momentarily 
by  pushing  the  rod  L,  a  knob  on  the  end  being  provided  for  the  purpose. 

Experiments  with  the  Self-Adjusting  1876  Injector.— In  the  experiments  made  with  the  injector 
described  above,  a  No.  6  instrument  was  employed,  selected  at  random  from  a  lot  in  stock.  It  was 
run  for  considerable  intervals  of  time  at  pressures  varying  by  10  lbs.  from  10  to  150  lbs.  per  square 
inch,  the  manipulation  described  above  being  observed  in  each  instance ;  and  at  all  pressures  the 
adjustment  of  the  water-supply  was  perfect  for  all  positions  of  the  starting-lever,  within  the  capacity 
of  the  instrument. 

Table  I.  shows  the  results  of  the  experiments  on  delivery  of  injector,  temperature  of  delivered  water, 
and  other  particulars,  which  are  fully  detailed  in  the  general  heading  and  in  the  several  columns.  For 
each  pressure  of  steam  noted  in  column  1,  the  water  was  delivered  by  the  injector  into  the  boiler 
under  approximately  the  same  pressure.  The  delivery  was  measured  by  observing  the  indications  of 
a  water-meter,  and  correcting  the  readings  as  already  described,  meter-readings  being  taken  at  fre- 
quent intervals,  and  each  experiment  being  continued  for  a  sufficient  length  of  time  to  obtain  a  num- 
ber of  duplicate  readings  for  equal  intervals.  The  pressures  in  column  8  were  obtained  by  throttling 
the  steam  supplied  to  the  injector,  and  observing  the  pressure  at  which  it  ceased  to  work,  each  experi- 
ment being  repeated  several  times  with  precisely  the  same  results.  The  temperatures  in  column  9 
were  obtained  by  gradually  heating  the  water  supplied  to  the  injector,  and  noting  the  temperature  at 
which  it  ceased  to  operate,  each  temperature  recorded  being  checked  by  several  repetitions  of  the 

Table  I. — Maximum  and  Minimum  Deliver)/  of  the  Self-adjusting  1876  Injector,  No.  6  ;  Temperature 
of  delivered  Water,  Pressure  against  which  Injector  delivers  Water,  and  highest  Temperature  ad- 
missible of  Feed.     Water  flowing  to  Injector  under  15  Inches  Head.      Waste -Valve  shut. 

Pressure  of 

Steam  supplied 

to  Injector, 

and  Pressure 

against  which 

Water  is 


Lbs.  per  Sq.  In. 



Pressure  of 
Steam  required 

to  deliver 

Water  against 

Pressure  in 

Column  1. 

admissible  of 



Ratio  of 

Minimum  to 



























Table  II.  shows  the  performance  of  the  injector  when  lifting  water  5  feet.  The  injector,  as  ordi- 
narily constructed  for  use  with  high-pressure  steam,  has  a  spindle  with  a  hole  which  is  rather  too 
small  for  low  pressures;  so  that  a  spindle  with  a  larger  opening  was  attached  in  all  but  the  last  expe- 
riment, when  the  high-pressure  spindle  was  replaced.  The  low-pressure  spindle  was  such  as  is  fitted 
in  injectors  designed  for  use  on  steamboats  and  other  places  where  the  pressure  is  ordinarily  less  than 
that  carried  in  locomotive  boilers. 

Table  II. — Maximum  and  Minimum  Delivery  of  the  Self-adjusting  1876  Injector,  No.  6  ;  Tempera- 
ture of  delivered  Water,  and  Pressure  against  ivhich  Injector  delivers  Water.  Feed-Water  lifted 
5  Feet.      Waste -Valve  closed. 

Pressure  of 
Steam  supplied 
to  Injector,  and 
Pressure  against 
which  Water 
is  delivered. 
Lbs.  per  Sq.  In. 



Pressure  of 
Steam  required 

to  deliver 

Water  against 

Pressure  in 

Column  1. 



Ratio  of 

Minimum  to 







1                      2 







30                      84. 8 
60                    114.2 
90                    137.7 
120                    150.7 
150                    150.7 













To  obtain  the  vacuum  in  the  supply-pipe,  as  recorded  in  Table  III.,  a  short  supply-pipe  was  used, 
having  a  vacuum-gauge  connected  to  it,  a  globe-valve  at  the  lower  end  of  the  pipe  being  immersed  in 
a  tank  of  water,  so  that  the  injector  and  supply-pipe  could  be  heated  by  blowing  steam  through  the 
supply-pipe,  and  could  be  cooled  quickly  to  ordinary  temperature  by  allowing  the  injector  to  draw 
water  from  the  tank. 

Table  III. —  Vacuum  in  the  Supply-Pipe  of  the  Self-adjusting  1876  Injector,  No.  6. 

Pressure  of 
Steam  supplied 

to  Injector. 
Lbs.  per  8q.  In. 




at  Ordinary 

Injector  and 

Supply-Pipe  as  Hot 

as  the  Steam  can 

make  them. 


at  Ordinary 

Injector  and 

Supply-Pipe  as  Hot 

as  the  Steam  can 

make  them. 












21 4 























Experiments  were  then  made  to  determine  the  steam-pressure  required  to  lift  water  and  start  the 
injector,  for  such  lifts  as  could  conveniently  be  obtained  in  the  testing-room,  by  throttling  the  steam 
until  the  lowest  pressure  at  which  the  injector  would  start  was  ascertained.  Using  the  high-pressure 
spindle,  the  pressure  required  for  a  lift  of  3  ft.  1  in.  was  38  lbs.  per  square  inch  ;  and  for  a  lift 
of  5  ft.,  47  lbs.  per  square  inch.  Lifting  with  this  pressure,  the  injector  delivered  water  against  a 
pressure  of  75  lbs.  per  square  inch. 

Having  started  the  injector  with  a  pressure  of  -17  lbs.  per  square  inch  and  a  lift  of  5  ft.,  the  steam- 
prcssure  was  gradually  reduced,  and  the  injector  continued  to  deliver  water  until  the  steam-pressure 
was  10  lbs.  per  square  inch,  the  water-pressure  being  17  lbs.  per  square  inch.  Using  the  low-pres- 
sure spindle  with  larger  hole,  the  Bteam-pressure  required  for  a  lift  of  5  ft.  was  30  lbs.  per  square 
inch.  The  injector  and  supply-pipe  were  then  heated  by  blowing  steam  into  the  tank,  and,  with  a 
steam-pressure  of  150  lbs.  per  square  inch  and  a  lift  of  4  ft.,  the  injector  was  started  in  3  seconds 
from  the  time  of  touching  the  Btarting-lever. 

Lifting  water  5  ft.,  the  highest  temperature  of  supply-water  with  which  the  injector  would  start 
was  as  follows :  With  the  high-pressure  spindle  ami  a  ^cam-pressure  of  120  lbs.  per  square  inch, 
highest  temperature  of  supply-water,  123°;  90  lbs.,  130°;  60  lbs.,  129°;  and  using  the  low-pressure 
spindle,  at  a  steam-pressure  of  30  lbs.,  101°. 

Experiments  on  the  least  pressure  with  which  the  injector  would  start,  the  water  flowing  to  it  under 
15  inches  head,  resulted  as  follow- : 

With  a  free  discharge  through  safety-valve  in  delivery-pipe,  equivalent  to  a  water-pressure  of  5  lbs. 
per  square  inch,  the  least  steam-pressure  with  which  the  injector  would  start  was  7  lbs.  per  square  inch. 
Discharging  into  the  boiler  against  a  pressure  equal  to  that  of  the  steam,  the  least  steam-pressure 
with  which  the  injector  would  start  was  8  lbs.  per  square  inch. 

When  the  injector  was  started,  delivering  water  against  a  pressure  of  5  lbs.  per  square  inch,  the 
steam-pressure  was  reduced  by  throttling  to  one  half  pound  per  square  inch  before  the  injector  ceased 
to  work. 

Lifting  5  ft.  with  a  steam-pressure  of  120  lbs.  per  square  inch,  and  a  supply-pipe  having  one  end 
free,  the  supply-pipe  was  violently  shaken  for  the  purpose  of  stopping  the  injector  if  possible.  It  was 
found  that  this  could  be  done,  but  only  by  a  peculiar  shock  of  great  violence — much  more  violent,  in 
fact,  than  would  ever  be  likely  to  occur  in  practice. 

Finally,  the  amount  of  water  wasted  in  starting  the  injector  was  carefully  measured,  the  average  of 
a  number  of  trials  being  36  cubic  inches,  or  about  1J  U.  S.  pint. 

2.  Tlie  Non- Adjustable  Injector  with  fixed  Nozzles,  non-lifting,  Figs.  2424  and  2425. — The  No.  6  in- 
jector of  this  variety  with  which  experiments  were  made  looks  externally  like  a  cylindrical  casting, 
open  at  one  end  for  connection  with  the  steam,  with  two  openings  in  the  shell  on  opposite  sides  for 
connection  with  supply  and  delivery  pipes,  and  a  waste-valve  which  can  be  turned  radially  so  as  to  dis- 
charge in  any  desired  direction,  and  can  be  shifted  so  as  to  discharge  on  either  side  of  the  shell. 
There  is  a  cap  on  the  other  end  of  the  shell,  and  when  this  is  removed  the  delivery  and  combining 
tubes  can  be  drawn  out  for  examination.  The  external  diameter  of  this  injector  is  70  millimetres, 
or  2.8  in.,  and  the  total  length  219.5  millimetres,  or  S.6  in.  It  is  apparently  about  as  compact  as 
such  an  instrument  can  well  be  made.  Indeed,  considering  the  appearance  of  injectors  as  ordinarily 
constructed,  this  instrument  might  readily  be  mistaken  for  a  steam-fitting.  In  its  action,  however, 
as  will  be  seen  by  reference  to  Table  IV.,  it  compares  very  favorably  with  larger  and  more  com- 



plicated  injectors.  This  injector,  being  non-adjustable,  and  having  no  valves  attached  to  it,  requires 
a  check-valve  in  the  delivery-pipe,  a  steam-stop  valve,  and  a  valve  to  regulate  the  amount  of  water 
supplied.  The  latter  valve  is  necessary,  because  this  injector,  like  all  others  having  fixed  nozzles,  if 
not  supplied  with  the  proper  amount  of  water  for  the  steam-pressure  under  which  it  is  working, 
will  leak  at  the  waste-valve  when  the  water-supply  is  too  great,  and  will  draw  in  air  if  the  water- 
supply  is  insufficient.  This  was  fully  proved  by  experiments  in  which,  the  injector  being  adjusted 
for  maximum  delivery  under  one  pressure,  the  pressure  was  then  varied,  with  the  results  just  noted. 
It  will  be  observed  in  Table  IV.  that  the  experiments  on  minimum  delivery  were  made  under  two 
conditions  in  several  instances — with  the  waste-valve  both  open  and  closed.  In  ordinary  practice, 
where  the  steam-pressure  is  not  maintained  sensibly  constant,  it  is  not  considered  desirable  to  work 
the  injector  with  the  waste-valve  closed. 

Table  IV. — Maximum  and  Minimum  Delivery  of  the  Fixed-Nozzle,  Non-lifting  Injector,  No.  6  ; 
Temperature  of  delivered  Water,  Pressure  against  lukich  Injector  delivers  Water,  and  Highest 
Temperature  admissible  of  Feed-  Water.      Water  flowing  to  Injector  under  15  Inches  Head. 

Pressure  of 

supplied  to 

and  Pressure 


which  Water 

is  delivered. 

Lbs.  per 

Sq.  In. 



of  Steam 


Tube  used. 








to  deliver 



DELIVERY.          Water 

1     against 



Waste  - 






Column  1. 




2           3 
















51. S 















The  manipulation  of  this  iujector,  although  not  as  simple  as  that  of  the  "  1876  "  instrument, 
presents  no  especial  difficulty.  It  is  necessary  to  open  the  water-supply  valve  sufficiently  to  deliver 
about  the  maximum  amount  of  water  that  the  injector  can  take  at  the  given  pressure,  and,  the  waste- 
valve  being  open,  as  soon  as  the  water  escapes  freely  through  the  waste-orifice,  to  open  the  steam- 
valve  slightly,  until  the  jet  is  established,  and  then  to  open  the  steam-valve  wide,  by  a  quick  motion. 
A  special  valve  is  provided,  as  illustrated  in  Fig.  2427,  for  facilitating  this  manipulation. 

Another  important  difference  between  the  injector  with  fixed  nozzles  and  the  self-adjusting  injector 
is  illustrated  by  comparing  the  maximum  delivery  of  the  two  injectors,  at  different  steam-pressures,  as 
recorded  in  column  2  of  Tables  I.  and  IV.  respectively.  It  will  be  seen  that  the  maximum  delivery 
of  the  self-adjusting  injector  increases  continually  with  increase  of  steam-pressure,  while  the  fixed- 
nozzle  injector  has  a  maximum  delivery  at  a  steam-pressure  depending  upon  the  proportions  of  the 



combining-tubc,  which  is  greater  than  the  maximum  delivery  for  any  other  steam-pressure,  cither 
higher  or  lower.  Thus,  it  appears  from  Table  IV.  that,  using  a  combining-tube  adapted  for  a  pres- 
sure of  70  lbs.  per  sq.  in.,  the  greatest  amount  of  water  is  delivered  by  the  injector  at  this  pressure ; 
and  that  on  replacing  this  combining-tube  by  one  adapted  to  a  steam-pressure  of  120  lbs.  per  sq.  in., 
similar  results  are  obtained — the  amount  of  water  delivered  by  the  injector,  in  eacli  instance, 
decreasing  as  the  steam-pressure  is  increased  beyond  the  point  for  which  the  combining-tube  is  pro- 
portioned? This  is  true  of  all  injectors  with  fixed  nozzles,  so  that  the  self-adjusting  injector  pos- 
sesses advantages  apart  from  the  ease  with  which  it  adapts  itself  to  varying  steam-pressure  and 
water-supply.  Still,  there  are  many  localities  where  injectors  can  be  worked  under  practically  con- 
stant conditions,  and  for  such  situations  the  non-adjustable  injector  is  well  adapted ;  while  the  sim- 
plicity of  this  particular  form,  and  the  ease  with  which  its  internal  parts  can  be  examined  and 
removed,  will  doubtless  prove  strong  recommendations. 

Although  this  injector  has  no  lifting  attachment,  it  can  be  made  to  lift  water  when  once  started 
under  a  head  in  the  supply-pipe.  This  was  illustrated  by  starting  the  injector  with  a  steam-pressure 
of  22  lbs.  per  sq.  in.,  the  water  flowing  to  it  under  15  inches  head,  and  then  suddenly  changing  the 
connections  so  that  the  supply  was  obtained  from  the  lower  tank  with  a  lift  of  3  ft.,  the  injector  con- 


tinning  to  deliver  water  under  these  conditions.  This  action  is  probably  the  same  as  that  of  a  siphon, 
which  will  continue  to  work  when  once  charged,  but  cannot  start  unless  the  pipe  is  first  filled. 
There  being  a  vacuum  at  some  point  of  the  delivery-tube  when  the  jet  is  established  and  the  injector 
is  at  work,  this  acts  in  a  similar  manner  to  the  long  leg  of  an  ordinary  siphon,  and  the  flow  continues. 
3.   The  Non-Adjustable  Injector,  with  fixed  Xozzles,  in  connection  with  a  Lifting  Attachment,  Figs. 

2426  and  2427. — Attached  to  one  side  of  this  injector  is  an  ejector  or  steam-siphon  which  draws 
water,  when  lifted  by  the  admission  of  steam,  through  the  combining-tube,  and  discharges  it  through 
the  orifice  of  the  lifting  attachment,  through  which  also  the  waste-overflow  takes  place.     This  injector 



has  a  check-valve  connected  to  it,  also  a  steam-stop  valve  which  can  be  opened  wide  by  half  a  revo- 
lution of  the  lever  on  the  stem.  In  connecting  the  injector,  since  it  has  fixed  nozzles,  a  water-supply 
valve  must  be  provided,  and,  as  already  .remarked,  a  second  check-valve  in  the  delivery-pipe  and 
another  steam-stop  valve  are  desirable. 

In  starting  this  injector,  steam  is  first  admitted  to  the  lifting-nozzle,  the  water-supply  valve  being 
adjusted  so  as  to  deliver  about  the  maximum  amount  of  water  corresponding  to  the  steam-pressure ; 
and  as  soon  as  solid  water  issues  from  the  lifting-nozzle,  the  steam-valve  is  to  be  opened  slightly 
until  the  jet  is  established,  when  the  full  steam-pressure  is  to  be  admitted,  and  the  valve  that  admits 
steam  to  the  lifting-nozzle  is  to  be  closed. 

Some  little  dexterity  is  required  to  start  the  injector  for  a  maximum  lift,  but  the  manipulation  is 
readily  acquired.  As  the  velocity  of  steam  escaping  from  an  orifice  varies  greatly  with  the  pressure, 
other  things  being  equal,  the  lifting-nozzle  must  have  proportions  depending  on  the  minimum  steam- 
pressure  to  be  employed,  since  it  can  readily  be  adapted  to  higher  pressures  by  partially  closing  the 
steam-admission  valve.  The  lifting-nozzle  on  the  injector  with  which  the  following  experiments  were 
made  was  proportioned  for  a  minimum  steam-pressure  of  60  lbs.  per  sq.  in. ;  and  it  was  found  that 
the  results  obtained  at  that  pressure  were  not  materially  exceeded  at  higher  steam-pressures,  while 
there  was  a  rapid  decrease  in  the  vacuum  and  lift  for  steam-pressures  below  60  lbs.  per  sq.  in. 

Table  V.  shows  the  vacuum  indicated  on  a  gauge  connected  to  the  supply-pipe  at  different  steam- 
pressures,  the  experiments  being  conducted  similarly  to  those  made  with  the  "  1876"  injector. 

Table  V. —  Vacuum  in  Supply-Pipe  of  the  Fixed-Nozzle  Lifting  Injector,  No.  6. 

Pressure  of  Steam  Supplied  to 


Lbs.  per  Square  Inch. 


Injector  at  Ordinary  Tempera- 

Injector  and  Supply-Pipe  as  Hot 
as  the  Steam  can  make  them. 







2  i 


It  is  considered  by  some  that  the  indications  of  a  vacuum-gauge  connected  to  the  supply-pipe  of  an 
injector  represent  the  actual  lift  that  can  be  obtained.  The  experiments  made  with  this  injector, 
however,  do  not  confirm  this  opinion.  For  the  purpose  of  ascertaining  the  maximum  lift,  the  injec- 
tor was  connected  at  the  top  of  the  scaffolding  to  which  reference  has  been  made,  and  the  heights 
to  which  water  could  be  lifted  and  delivered  were  carefully  measured,  the  lifts  being  varied  by 
changing  the  length  of  the  supply-pipe,  the  boiler-pressure  being  also  varied  for  each  lift,  until  a 
steam-pressure  was  reached  at  which  the  injector  would  raise  and  deliver  the  water.  The  results  of 
these  experiments  are  contained  in  Table  VI.  It  will  be  seen  that  no  advantage  was  derived  from 
increasing  the  steam-pressure  beyond  60  lbs.  per  sq.  in.,  while  the  decrease  in  lift  was  rapidly  accel- 
erated as  the  steam-pressure  was  reduced.  It  is  believed  there  were  no  leaks  in  the  supply-pipe 
used  in  these  experiments,  but  the  greatest  lift  obtained  is  by  no  means  an  equivalent  for  the  best 
vacuum  recorded  in  Table  V.  This  suggests  that  records  of  lifts  based  on  the  indications  of  a 
vacuum-gauge  may  not  be  very  reliable. 

Table  VI. — Steam-Pressure  required  to  lift  and  deliver  Water  with  the  Fixed-Nozzle  Lifting  Injec- 
tor, No.  6. 

Height  Water  ts  lifted. 

Steam-Pressure  required  to 
lift  and  deliver  Water. 

Height  Water  is  lifted. 

Steam-Pressure  required  to 
lift  and  deliver  Water. 

Feet.  Inches. 
3        0 
5        0 
11        6 
15        0 

Lbs.  per  Square  Inch. 

Feet.   Inches. 

21  3 

22  10              < 

Lbs.  per  Square  Inch. 



On  the  completion  of  the  experiments  just  described,  the  lifting-nozzle  was  replaced  by  one 
adapted  to  a  lower  steam-pressure,  and  the  injector  was  started  with  a  steam-pressure  of  49  lbs.  per 
square  inch,  and  a  lift  of  21  ft.  10  in. ;  after  which  the  steam  was  throttled,  the  water-pressure  being 
similarly  reduced,  the  injector  continuing  to  work  until  the  steam-pressure  was  reduced  to  7  lbs.  per 
square  inch,  the  water-pressure  being  10  lbs.  From  this  it  will  be  seen  that  by  the  aid  of  a  priming 
attachment  the  injector  could  be  started  at  a  much  lower  steam-pressure  than  that  for  which  the 
lifting-nozzle  is  adapted 

Duty  of  Sellers  Injectors, — A  final  note  in  relation  to  the  duty  of  injectors,  or  the  foot-pounds  of 
useful  work  performed  by  the  consumption  of  100  lbs.  of  coal  in  the  boiler  supplying  steam  to  the 
injector,  may  be  of  interest.  When  the  evaporation  of  the  boiler  is  known,  this  duty  can  readily  be 
computed  from  the  data  obtained  in  connection  with  the  maximum  delivery  of  the  injector.  This 
can  be  illustrated  by  an  example,  assuming  the  boiler  evaporation  at  9  lbs.  of  steam  per  lb.  of  coal, 
a  result  which,  though  rather  above  the  average,  is  occasionally  exceeded  in  good  practice.  Using 
the  data  recorded  in  Table  I.  for  the  maximum  delivery  at  a  steam-pressure  of  130  lbs.  per  sq.  in.,  it 
appears  that  150—66  =  8-1  units  of  heat  were  imparted  to  each  pound  of  water  delivered  by  the 
injector,  and,  the  weight  of  a  cubic  foot  of  water  at  a  temperature  of  66°  F.  being  about  62.3  lbs., 
that  the  total  weight  of  water  delivered  per  hour  was  161.2  x  62.3  =  10,042.76  lbs. ;  so  that  the 
total  amount  of  heat  imparted  to  the  water  per  hour  was  10,042.76  x  84  =  843,591.84  units. 



The  total  heat  above  32°  in  a  pound  of  dry  steam,  at  a  pressure  of  180  lbs.  per  sq.  in.,  is  1,187.8 
units,  and  the  heat  remaining  in  a  pound  of  steam  above  32°,  after  condensation,  was  150—32  =118 
units;  so  that  each  pound  of  dry  steam  imparted  1187.8— .118  =  1,069.8  units  of  heat  to  the  feed- 


water,  and  the  weight  of  dry  steam  required  per  hour  was 


=  788.6  lbs. 

column  of  water  equivalent  to  the  pressure  against  which  the  water  was  delivered  was 

The  height  of  a 
144  x  130 _ 

300.5  ft.,  so  that  the  useful  work  performed  per  hour  was  10,042.76  x  300.5  =  3,017,049.38  foot- 
pounds. The  weight  of  coal  required  to  do  this  work,  on  the  assumed  boiler  evaporation,  was  -  = 
87.6,  so  that  the  duty  of  the  injector,  per  100  lbs.  of  coal,  was  — —  ~~oS~^ =  3,455,536  foot- 

The  Hancock  Inspirator. — An  elaborate  scries  of  trials  of  this  apparatus  was  made  by  Park 
Benjamin's  Scientific  Expert  Office  of  New  York,  to  obtain  new  data  for  the  present  work,  at  the 
factory  of  the  Hancock  Inspirator  Company  in  Boston,  in  May,  1879.  The  experiments  were  con- 
ducted by  Richard  II.  Buel,  C.  E.,  and  the  report  is  appended. 

Report  of  Trials  of  Hancock  Inspirator. 

The  Hancock  inspirator  differs  in  some  important  respects  from  the  instruments  commonly  classed 
under  the  head  of  injectors.  It  consists  essentially  of  a  lifting-jet  and  lifting-nozzle,  combined  with 
a  forcing-jet  and  force-nozzle  or  injector,  steam  being  admitted  to  both  of  these  nozzles  whenever 
the  inspirator  is  in  operation,  to  deliver  the  supply-water  to  the  force-nozzle,  and  to  force  it  through 
this  nozzle  into  the  boiler.    Although  both  the  lifting-  and  force-nozzles  are  fixed,  their  proportion  one 


to  the  other  is  such  that  the  inspirator  requires  no  adjustment  for  changes  in  steam-pressure  or  water- 
supply,  the  waste-valve  being  kept  closed  while  the  instrument  is  in  operation,  except  at  the  time  of 
starting.  The  sectional  view  of  the  stationary  inspirator,  Fig.  2428,  will  serve  to  explain  the  action 
of  the  instrument.     In  this  figure,  A  is  the  steam-supply  pipe,  connected  to  the  steam-space  of  the 



boiler ;  B  is  the  water-supply  pipe ;  and  C  is  the  feed-pipe,  to  which  is  connected  an  overflow  or 
waste-pipe  with  waste-valve,  these  latter  connections  not  being  shown  in  the  figure.  I)  is  the  lifting- 
jet,  E  the  lifting-nozzle,  G  the  forcing-jet,  and  H  the  force-nozzle.  This  latter  nozzle  is  somewhat 
analogous  to  the  combining-tube  of  an  ordinary  injector.  F  and  /  are  stop-valves,  the  first  controlling 
the  admission  of  steam  to  the  forcing-jet,  and  the  latter  determining  the  course  of  the  water  delivered 
by  the  lifting-jet.  The  action  of  the  inspirator  can  perhaps  be  most  simply  explained  in  connection 
with  a  description  of  the  manipulation  required  to  start  the  instrument.  In  the  figure,  the  inspira- 
tor is  represented  in  operation ;  but  when  it  is  not  working,  a  steam-valve  in  the  pipe  A,  not  shown, 
is  closed,  as  is  also  the  valve  F,  while  the  valve  /  and  the  waste-valve  are  open.  Opening  the  valve 
in  the  steam-supply  pipe  A,  steam  is  admitted  to  the  lifting-jet  D,  drawing  water  through  the  supply- 
pipe  B,  and  discharging  it  through  the  lifting-nozzle  E,  valve  I,  waste-valve,  and  overflow-pipe.  As 
soon  as  water  issues  from  the  overflow-pipe,  the  valve  i"  is  to  be  closed,  when  the  supply-water  will 
pass  through  the  force-nozzle  H,  and  will  escape  at  the  overflow.  The  valve  F  is  then  to  be  opened, 
by  moving  the  lever  K  one  quarter  turn,  and  the  waste-valve  is  to  be  closed,  when  the  water  lifted 
and  delivered  to  the  force-nozzle  H  will  be  forced  into  the  boiler  by  the  steam  issuing  from  the 
forcing-jet  G.  If  the  water-supply  is  to  be  varied,  this  can  be  effected  by  partially  closing  a  valve 
in  the  supply-pipe  B,  without  throttling  the  admission  of  steam ;  or  both  the  steam  and  water  may 
be  throttled  if  desired.  In  practice,  however,  the  delivery  is  varied  by  throttling  the  water-supply. 
Whatever  changes  of  adjustment  are  made,  whether  of  steam-  or  water-supply  valves,  within  the 
capacity  of  the  inspirator,  the  instrument  will  continue  in  operation  with  the  waste-valve  closed. 
In  this  respect  the  inspirator  differs  materially  from  fixed-nozzle  injectors,  which  cannot  be  operated 
with  the  waste  closed,  under  the  conditions  recited  above. 

The  principle  of  the  locomotive  inspirator,  Figs.  2429  and  2430,  is  the  same  as  that  of  the  station- 
ary inspirator  just  described,  but  the  arrangement  is  such  that  all  the  operations^  starting^  and 
stopping  can  be  performed  by  the  movement  of  a  single  lever ;  and  the  instrument  is  self-contained, 
being  ready  for  attachment  without  the  use  of  additional  valves.  A  slight  movement  of  the  starting- 
lever^  admits  steam  to  the  lifting-jet.  When  water  issues  from  the  overflow,  a  further  movement  of 
the  starting-lever  closes  one  of  the  valves,  thus  turning  the  supply-water  through  the  force-nozzle, 
admits  steam  to  the  forcing-jet,  and  closes  the  waste-valve,  thus  starting  the  instrument.  In  attach- 
ing this  instrument  to  a  locomotive,  it  is  usual  to  place  a  "  lazy-cock  "  in  the  supply-pipe,  by  means 
of  which  the  engine-runner  can  control  the  water-supply  without  changing  the  position  of  the  start- 
ing-lever. . 

In  the  tests  made  with  the  inspirator,  both  forms,  as  described  above,  were  tried,  the  size  ot  the 
instruments  being  No.  30,  this  indicating  that  the  smallest  diameter  of  the  force-nozzle  was  0.30  of 
an  inch.  This  dimension  was  carefully  checked  by  measurement.  But  one  inspirator  of  each  form, 
locomotive  and  stationary,  was  used  in  the  experiments,  and  no  changes  of  any  kind  were  made  in 
them  during  the  trials.  "  Some  of  the  results  of  the  trials  are  contained  in  Tables  VII.  and  VIII., 

Table  VII. — Maximum  and  Minimum  Delivery  of  the  Hancock  Stationary  Inspirator,  No.  30,  lifting 
Water  from  2  to  3  Feet ;  Temperature  of  delivered  Water  ;  Vacuum  in  Supply-Pipe  ;  and  rela- 
tive Steam-  and  Water-Pressures  under  which  Inspirator  mill  deliver  Water.  Temperature  of 
Supply-Water,  70°  F. 

Pressure  of 
Steam  supplied 
to  Inspirator, 
and  Pressure 
against  which 


delivers  Water. 

Lbs.  per 

Square  Inch. 



Vacuum  in 

Inches  of 


St  earn -Pressure 

with  which 


will  deliver 

Wuter  against 

Pressure  in 

Column  1. 

Lbs.  per  Sq.  In. 


wide  open, 
and  Supply 

Ratio  of 

Minimum  to 





wide  open, 
and  Supply 


throttled,  and 


wide  open. 












60. S 












and  the  manner  of  obtaining  the  quantities  in  the  several  columns  will  be  briefly  detailed.  The 
steam-  and  water-pressures  were  measured  by  gauges  made  by  the  Crosby  Steam  Gauge  and  Valve 
Company  of  Boston.  These  gauges  were  tested  by  their  manufacturers  immediately  before  the 
trial,  and  were  certified  to  be  correct.  The  temperature  of  delivered  water  was  measured  by  a 
thermometer  inserted  in  the  delivery-pipe,  close  to  the  inspirator.  All  the  thermometers  used  in 
the  tests  were  made  by  Huddleston  of  Boston,  and  were  carefully  tested.  In  determining  the  tem- 
peratures at  maximum  and  minimum  delivery,  the  water  was  forced  into  the  boiler  furnishing 
steam  to  the  inspirator,  and  the  results  in  Table  VIII.  and  in  column  9,  Table  VII.,  were  deter- 
mined under  the  same  conditions.  The  boiler  used  in  the  experiments  was  of  the  sectional  vari- 
ety, and  quite  small,  the  grate-surface  being  only  6.25  feet.  Considerable  difficulty  was  experi- 
enced in  maintaining  the  steam-pressure  steady  when  forcing  water  into  it  by  the  inspirator  that 



was  being  tested,  so  that,  in  the  capacity  experiments,  the  results  of  which  will  be  found  in  col- 
umns 2  and  3,  Table  VII.,  the  delivered  water  was  run  to  waste,  being  throttled  in  the  delivery- 
pipe  until  the  water-pressure  was  equal  to  that  of  the  steam  supplied  to  the  inspirator.  The 
use  of  so  small  a  boiler,  apart  from  its  inconvenience,  was  decidedly  unfavorable  to  the  perform- 
ance of  the  inspirator,  as  considerable  water  was  entrained  with  the  steam,  owing  to  the  severe 
drain  upon  the  boiler.  To  determine  the  quantity  of  water  delivered  by  the  inspirator,  the  supply- 
water  was  drawn  from  a  tank  which  was  supported  upon  platform  scales,  and  the  time  required  to 
deliver  a  given  weight  was  measured  by  a  stop-watch,  the  experiments  being  repeated  several  times, 
at  each  pressure,  in  order  to  check  the  results.  The  vacuum  in  the  supply-pipe  was  measured  by 
attaching  a  vacuum-gauge  to  a  short  supply-pipe  immersed  in  water,  and  nearly  closing  the  water- 
supply  valve.  The  highest  admissible  temperature  of  supply-water  was  measured  by  a  thermometer 
placed  in  the  supply-pipe,  close  t<>  the  inspirator,  the  supply-water  being  lifted  from  a  barrel,  and  its 
temperature  being  regulated  by  mixing  hot  and  cold  water  in  the  supply-pipe.  The  accuracy  of  this 
method  of  trial  was  also  cheeked  by  gradually  beating  the  water  in  the  barrel  until  a  point  was 
reached  at  which  the  inspirator  would  no  longer  work. 

Table  VIII. — Highest  Temperature  admissible  for  Supply-Water,  lifted  2  Feet,  by  the  Hancock  Sta- 

Honary  Inspirator,  Ko.  30. 

Pressure  of  Steam 

■  Inspirator, 
und  Pressure  agalns! 

which    [n 

delivers  Water. 
Lbs.  per  Square  Inch. 

Highest  Temperature 
of  Supply  -Water 



Fahrenheit  Degrees. 

Temperature  of 

delivered  Water,  when 
Supply-Walt  r  i'  .t 
the  highest  Admissible 

I        n  rature. 
Fahrenheit  Degrees. 

Pressure  of  Stenm 
supplied  to  Inspirator, 
and  Pressure  i 

whieh  Inspirator 

delivers  Water. 

Lbs.  per  Square  Inch. 

Hiphest  Temperature 
of  Supply-Water 


Temperature  of 

delivered  Water,  when 

Supply-Water  is  at 

the  highest  admissible 

Fahrenheit  Degrees. 






















In  some  further  trials  of  this  inspirator,  on  June  11  and  12,  1879,  lifting-jets  and  nozzles  of  differ- 
ent proportions  were  used,  with  the  following  results:  At  a  steam-pressure  of  50  lbs.  per  square  inch, 
the  maximum  temperature  of  supply-water  admissible  was  161  ;  at  60  His.,  146' ;  80  lbs.,  147°;  90 
lbs.,  145°;  100  lbs.,  143J  ;  110  lbs.,  Ill;  120  lbs.,  146  .  Experiments  were  also  made  at  different 
rate-  of  delivery  ;  and  it  was  found  that  the  maximum  temperature  admissible  for  the  supply-water 
was  practically  the  same  whether  the  inspirator  was  working  with  a  minimum  or  maximum  delivery. 

In  addition  to  the  experiments  already  described,  the  results  of  which  are  contained  in  Tallies  VII. 
and  VIII.,  other  trials  were  made,  which  are  detailed  below. 

Delivering  water  against  a  pressure  equal  to  that  of  the  steam,  the  temperature  of  supply-water 
being  69°,  and  the  lift  2  feet,  the  lowest  pressure  at  which  the  inspirator  would  start  was  12  lbs. 
per  square  inch  with  a  free  supply,  and  9  lbs.  with  the  supply  throttled.  Once  started,  and  delivering 
under  a  free  discharge,  the  inspirator  continued  to  work  as  long  as  there  was  any  indication  of  pres- 
sure on  the  Steam-gauge.  Delivering  against  a  water-pressure  of  5  lbs.  per  square  inch,  the  inspira- 
tor continued  to  work  until  the  steam-pressure  was  reduced  to  1  lb. 

Experiments  were  also  made  to  determine  the  time  in  which  the  inspirator  could  be  started,  when 
both  the  instrument  and  the  supply-pipe  were  heated  by  allowing  steam  to  flow  through  for  a  short 
time.  With  the  stationary  inspirator,  lifting  water  from  2  to  3  feet,  allowing  steam  to  flow  through, 
and  then  starting  the  instrument  at  once,  without  closing  the  steam-valve,  the  time  required  to  start 
was  ItH  seconds  when  the  temperature  of  the  supply-water  was  116°,  and  6£  seconds  when  the  tem- 
perature of  the  supply-water  was  76°,  the  steam-pressure  being  95  lbs.  per  square  inch,  and  the 
water-pressure  the  same. 

Using  the  locomotive  inspirator,  with  a  lift  of  Si  feet,  steam-pressure  of  125  lbs.  per  square  inch, 
water-pressure  1(50  lbs.,  and  supply-water  70  ,  the  time  required  to  start,  after  heating  the  instru- 
ment and  supply-pipe  as  hot  as  the  steam  could  make  them,  was  2  seconds.  With  a  lift  varying 
between  2  and  3  feet,  and  a  steam-  and  water-pressure  of  95  lbs.  per  square  inch,  it  was  found  that 
the  inspirator  would  start  promptly  (not  a  single  failure  occurring)  with  supply-water  heated  to  the 
highest  temperature  admissible  for  regular  working.  At  these  moderate  lifts  it  was  found  that  the 
water  could  be  taken  by  the  lifter,  and  discharged  at  the  waste  orifice,  at  much  higher  temperatures 
than  were  admissible  for  the  operation  of  the  inspirator — the  temperature  of  the  supply-water  being 
raised  to  195"  without  sensibly  affecting  the  prompt  action  of  the  lifter. 

A  number  of  trials  were  made  to  determine  the  amount  of  water  wasted  in  starting  the  locomotive 
inspirator,  and  the  average  was  1.15  U.  S.  quart. 

The  stationary  inspirator  was  fitted  up  with  a  supply-pipe  having  considerable  flexibility  by  reason 
of  two  right-angled  bends,  and  attempts  were  made  to  stop  the  operation  of  the  instrument  by  strik- 
ing and  jarring  the  supply-pipe,  the  steam-  and  water-pressure  being  130  lbs.  per  square  inch,  and 
the  lift  3  feet.  After  extraordinary  exertions,  the  jet  was  broken  in  a  single  instance,  and  the 
inspirator  stopped,  but  only  by  straining  the  connections  to  such  an  extent  that  it  was  considered 
unsafe  to  repeat  the  experiment.  The  supply-pipe  was  jarred  by  heavy  blows  applied  at  various 
points,  without  affecting  the  operation  of  the  inspirator. 


The  results  of  the  experiments  in  Table  VII.  show  that  the  inspirator  requires  no  adjustment  for 
changes  in  steam-pressure  and  water-supply  ;  and  a  further  experiment  was  made  by  simultaneously 
reducing  the  steam-  and  water-pressure  from  150  to  2|  lbs.  per  square  inch,  keeping  the  waste- 
valve  closed,  without  adjusting  either  the  steam-  or  water-supply.  This  experiment  affords  addi- 
tional proof  in  regard  to  the  adaptability  of  the  instrument  to  varying  conditions  of  pressure. 

After  completing  the  experiments  already  described,  the  stationary  inspirator  was  connected  25 
ft.  above  a  tank,  and  was  started,  with  a  steam-pressure  of  50  lbs.  per  square  inch,  delivering 
against  an  equal  water-pressure.  The  water-pressure  was  then  increased  to  80  lbs.  per  square  inch 
before  the  inspirator  ceased  to  work.  The  temperature  of  the  delivered  water  in  this  experiment 
was  156°.  Again  starting  the  inspirator  at  25  ft.  lift,  and  steam-  and  water-pressure  of  50  lbs. 
per  square  inch,  these  pressures  were  gradually  reduced,  and  the  inspirator  continued  to  operate  as 
long  as  there  was  any  indication  of  pressure  in  the  steam-gauge,  the  water-pressure  being  2^  lbs.  per 
square  inch. 

The  inspirator  is  sometimes  used  to  elevate  water  into  tanks,  using  the  lifting-jet  only.  With  a 
lift  of  25£  ft,,  the  temperature  of  the  delivered  water  was  only  increased  from  70°  to  83°. 

Experiments  were  also  made  upon  the  ease  of  starting  the  inspirator  at  a  lift  of  25  ft.  With  the 
inspirator  and  supply-pipe  at  ordinary  temperature,  the  time  required  to  lift  the  water  was  10| 
seconds  ;  and  to  start  the  instrument,  the  steam-  and  water-pressure  being  50  lbs.  per  square  inch, 
the  time  required  was  21+  seconds.  The  inspirator  and  supply-pipe  were  then  heated  by  blowing 
through,  and  water  was  lifted  in  48i  seconds.  These  trials,  together  with  those  made  at  low  lifts 
previously  detailed,  show  the  remarkable  promptness  of  the  instrument  in  starting,  under  all  condi- 
tions within  its  capacity. 

The  lifting-jet  used  in  these  experiments  was  proportioned  for  a  steam-pressure  of  60  lbs.  per 
square  inch ;  and  to  show  the  range  of  this  jet,  after  the  inspirator  had  been  started  on  a  25 -ft. 
lift,  the  steam-  and  water-pressure  were  simultaneously  increased  to  SO  lbs.  per  square  inch  before 
the  jet  broke.  Reducing  the  lift  to  24  ft.,  the  steam-pressure  required  to  start  against  an  equal 
water-pressure  was  45  lbs.  per  square  inch,  and  the  range  was  considerably  increased,  the  steam- 
and  water-pressure  being  varied  to  100  lbs.  per  square  inch  before  the  jet  broke.  With  a  lift  of  24 
ft.,  and  steam-  and  water-pressure  of  50  lbs.  per  square  inch,  the  water  in  the  supply-pipe  was 
heated  to  117°  before  the  inspirator  ceased  to  work. 

On  June  11,  1879,  some  experiments  were  made  with  a  stationary  inspirator,  No.  20,  at  higher 
lifts  than  had  been  previously  employed.  The  lifting-jet  used  was  proportioned  for  a  steam-pressure 
of  about  60  lbs.  per  square  inch,  at  a  maximum  lift ;  and  the  results  of  the  trials  are  appended. 
For  a  lift  of  26  ft.  7  in.  the  steam-pressure  required  to  start  the  inspirator  was  60  lbs.  per  square 
inch,  and  the  time  employed  in  starting  was  :  From  time  of  opening  steam-valve  to  lifting  water,  10 
seconds ;  and  from  time  of  opening  steam-valve  until  inspirator  was  in  operation  with  a  water-pres- 
sure equal  to  that  of  the  steam,  38  seconds.  After  the  inspirator  was  started  the  water-pressure  was 
increased  to  95  lbs.  per  square  inch,  the  steam-pressure  being  60  lbs.,  before  the  jet  broke.  The  lift 
was  then  increased  to  27  ft.,  and  the  inspirator  lifted  water  in  11  seconds  with  63  lbs.  of  steam,  and 
delivered  water  against  a  pressure  equal  to  that  of  the  steam  in  52|  seconds.  The  water-pressure 
was  then  increased  to  95  lbs.  per  square  inch  before  the  jet  broke ;  and  to  show  the  range  of  this 
particular  lifting-jet,  the  steam-  and  water-pressure  were  simultaneously  reduced  to  10  lbs.  per  square 
inch,  and  then  increased  to  70  lbs.  before  the  inspirator  ceased  to  operate. 

The  Injector,  considered  as  a  Pcmping  Engine,  is  not  an  economical  machine,  as  will  appear 
from  the  calculations  on  page  169.  As  a  boiler-feeder,  however,  it  is  more  economical  than  a 
steam-pump,  when  cold  feed-water  is  used,  since,  although  but  little  of  the  heat  of  the  steam  is  con- 
verted into  useful  work,  nearly  all  the  remainder  is  returned  to  the  boiler  with  the  feed-water.  In 
its  present  improved  form,  the  injector  is  rapidly  superseding  the  pump  on  locomotives,  and  to  a  con- 
siderable extent  on  stationary  and  steamship  boilers  also. 

INSULATORS.     See  Telegraph  Apparatcs. 

IRONCLAD  VESSELS.     See  Armor. 

IRONING  MACHINE.     See  Laundry  Machinery. 

IRON-MAKING  PROCESSES.  The  various  processes  of  iron-making,  by  which  is  here  under- 
stood the  production  of  wrought  iron  from  iron  ore,  are  divided  into  two  classes,  the  direct  and  the 
indirect.  The  direct  processes  are  those  in  which  the  ore  is  converted  in  one  or  more  operations 
into  wrought  iron,  without  being  first  converted  into  cast  iron.  The  indirect  processes  are  those  in 
which  the  ores  are  first  smelted  in  a  blast-furnace,  forming  pig  iron  or  cast  iron,  and  the  pig  iron  is 
then  converted  by  a  subsequent  process  into  wrought  iron.  For  the  method  of  making  cast  iron, 
see  Furnace,  Blast,  and  Furnace,  Cupola  ;  for  other  subjects  more  or  less  directly  related  to  iron- 
making,  see  Forge,  Forging,  Furnaces,  Hammers,  Punching  and  Shearing  Machinery,  and  Steel. 

In  the  blast-furnace,  iron  ores— containing  oxygen  in  combination  with  the  iron,  together  with  vari- 
ous earthy  impurities — are  first  deoxidized,  and  the  impurities  are  then  removed  by  fluxing.  The 
iron  is  then  impregnated  with  from  2  to  5  per  cent,  of  carbon,  a  smaller  percentage  usually  of  sili- 
con, and  still  smaller  percentages  or  traces  of  other  impurities,  as  sulphur  and  phosphorus;  then 
melted  and  run  out  of  the  furnace  in  the  shape  of  pig  iron.  In  the  subsequent  conversion  of  pig 
iron  into  wrought  iron,  the  carbon,  silicon,  and  other  impurities  are  removed,  and  the  resulting  pro- 
duct, wrought  iron  (sometimes  called  malleable  iron,  also  weld  iron),  consists  of  iron  with  very  small 
proportions  of  impurities.  The  methods  by  which  this  conversion  is  accomplished  include  what 
are  known  as  the  finery  and  the  puddling  processes,  which  are  treated  of  hereafter.  By  the  Besse- 
mer and  Siemens-Martin  steel  processes  pig  iron  is  also  decarbonized  and  freed  from  impurities, 
forming  a  product  which  may  be  as  pure  as  or  even  purer  than  wrought  iron,  to  which  the  names  of 
mild  steel,  homogeneous  metal,  and  ingot  iron  are  variously  applied. 

In  this  article  the  several  direct  processes  will  be  described,  also  those  indirect  processes  whose 



object  is  the  conversion  of  pig  into  wrought  (weld)  iron.  Those  indirect  processes,  including  the 
Bessemer  and  Siemens-Martin  processes,  whose  object  is  the  conversion  of  pig  iron  into  mild  steel 
(ingot  iron)  are  treated  of  in  the  article  on  Steel. 

I.  Direct  Processes. 

The  direct  processes  of  making  wrought  iron  are  both  ancient  and  primitive.  Records  of  these 
processes  date  back  to  the  earliest  historical  times,  and  processes  almost  exactly  similar  to  the 
ancient  ones  are  still  in  use  in  uncivilized  countries,  and  to  a  small  extent,  for  the  manufacture  of 
iron  of  certain  grades,  in  the  United  States.  The  direct  processes  have  been  almost  entirely  super- 
seded in  modern  times  by  the  indirect ;  not  however  on  account  of  the  improved  quality  of  the  pro- 
duet  of  the  latter,  but  on  account  of  its  cheapness.  In  recent  times  many  efforts  have  been  made 
so  to  improve  the  economy  of  the  direct  processes  that  they  may  make  iron  more  cheaply  than  the 
indirect,  but  thus  far  without  success,  except  under  the  most  favorable  conditions  in  a  very  few 

In  the  most  primitive  processes,  such  as  those  which  are  still  used  in  Asia  and  Africa,  scarcely  any 
other  apparatus  is  needed  than  a  small  hearth,  or  a  hole  in  the  ground,  with  or  without  a  chimney. 
An  air-blast  is  furnished  by  a  bellows  or  other  simple  blowing  machine.  Only  rich  ores  are  used, 
and  the  fuel  is  invariably  charcoal.  A  furnace  of  this  kind,  still  used  in  Fcrsia,  consists  of  a  mere 
cavity  in  the  earth,  6  to  12  in.  deep,  and  of  a  diameter  equal  to  twice  the  depth.  It  is  lined  with 
pulverized  charcoal.  Charcoal  in  fragments  is  then  thrown  in,  and  covered  with  ore,  which  may  be 
fine  and  caked  together  with  water,  or  in  coarse  pieces.  Several  alternate  layers  of  charcoal  and  ore 
succeed,  when  the  whole  heap  is  covered  with  charcoal.  It  is  then  fired  at  the  bottom,  and  the 
blast  applied  by  a  huge  hand-bellows,  which  blows  through  a  pipe  introduced  in  the  lower  part.  In 
a  few  hours  a  small  ball,  or  hup,  is  obtained,  which  is  taken  out  and  hammered  by  hand.  By  reheat- 
ing and  hammering  it  is  finally  brought  into  shape,  and  purified  of  cinder.  The  process  is  such  as 
may  lie  practised  on  a  smaller  scale  in  a  blacksmith's  forge.  Figs.  2481  and  2432  are  respectively  a 
section  and  a  ground  plan  of  a  hearth  in  use  in  Europe  about  the  middle  of  the  10th  century,  as 
described  by  Agricola.  The  letter  h  in  both  shows  the  hearth  proper,  /  the  tuyere,  and  b  the  bellows. 
This  form  is  not  unlike  the  blacksmith's  forge  of  our  own  times,  and  the  furnaces  used  in  the 


Catalan  process  at  the  present  day  are  but  modifications  of  it.  These  crude  furnaces  show  that  the 
production  of  iron  from  the  ore  is  a  process  of  the  most  simple  description.  The  quality  of  the  iron 
produced  in  them  also  is  not  surpassed,  and  rarely  even  equalled,  by  that  made  by  the  most  ap- 
proved methods  of  modern  times.  The  enormous  progress  in  iron-making  during  the  last  three 
hundred  years,  and  especially  within  the  present  century,  has  been  in  the  direction  of  quantity  and 
cheapness,  and  not  in  that  of  improved  quality. 

The  Catalan  Process. — This  process  derives  its  name  from  the  province  of  Catalonia,  in  northern 
Spain,  where  probably  it  was  first  introduced  into  western  Europe.  The  furnace  in  which  it  is  car- 
ried on  is  known  as  the  Catalan  forge,  although  the  names  open  fire,  forge,  German  forge,  and 

bloomary  are  often  indiscriminately 
24:33.  applied  to  it.    Some  writers  make  dis- 

tinctions between  the  various  types 
of  furnace  to  which  these  names  may 
be  correctly  applied,  but  they  are  not 
important,  and  the  same  name  is  ap- 
plied to  different  types  of  furnaces  in 
different  localities.  The  term  bloom- 
ary is  also  applied  to  a  furnace  which, 
while  somewhat  similar  in  shape  to 
the  Catalan  forge,  is  used  for  a  differ- 
ent purpose,  viz.,  the  conversion  of 
pig  iron  into  wrought  iron.  It  is  de- 
scribed under  the  head  of  the  finery 

The  simplest  form  of  the  Catalan 
forge,  as  still  used  in  the  Pyrenees,  is 
shown  in  Figs.  2433,  2434,  and  2435. 
Fig.  2433  is  a  vertical  section  through  the  axis  of  the  tuyere,  and  Fig.  2434  another  section  at 
right  angles  to  the  former.  In  Fig.  2433,  IF  W  represents  the  wall  separating  the  forge  from  the 
blast  machinery,  and  in  which  is  the  embrasure  for  the  tuyere.     The  hearth  is  usually  lined  with 



cast-iron  plates,  and  the  counter,  or  side  opposite  the  tuyere,  with  flat  bars.  Sometimes  the  lining  of 
these  is  a  refractory  sandstone  or  granite ;  but  the  cinder-slope  (on  the  side  o  of  the  tuyere),  on 
which  the  workman  rests  his  bars,  is  alwavs  of  cast  iron.  The  aperture  o  is  for  the  discharge  of 
cinder  into  the  embrasure  beneath.     The  tuyere  t  is  a  truncated  half  cone  of  copper,  with  the  orifice 



'^  vr^t^^vi..  -.,,-,•„  ..,'v.^ 

or  eye  circular,  from  U  to  2  in.  in  diameter;  it  is  set  at  about  20  in.  above  the  bottom,  and  inclined 
at  an  ande  of  30°  to  40°,  and  projects  about  8  in.  into  the  fire.  The  hearth  at  the  bottom  measures 
about  2A0  26  in.  square.  Blast  is  furnished  either  by  a  bellows,  or  by  the  blowing  machine  driven 
by  water-pressure  known  as  the  trompe.  (See  Blowers.)  In  the  operations  of  the  forge  as  usually 
conducted,  a  charge  of  about  1,000  lbs.  of  ore  is  weighed  out  and  crushed  under  the  forge-hammer. 
The  furnace  having  been  heated,  and  a  mass  of  incandescent  charcoal  and  melted  cinder  lying_  upon 
the  bottom,  fresh  charcoal  is  packed  in  the  hearth  up  to  the  orifice  of  the  tuyere,  and  upon  this  bed 
a  box  of  coarse  ore  is  emptied  and  packed  against  the  sloping  side  or  counter,  charcoal  alternating 
with  fine  ore  being  packed  on  the  tuyere  side.  The  blast  is  started  at  a  light  pressure,  gradually 
increasing  to  about  14  lb.  per  square  inch.  The  whole  of  the  contents  of  the  hearth,  except  a  small 
portion  at  the  sloping"  side  on  which  the  coarse  ore  is  placed,  are  kept  covered  with  fine  ore  and  char- 
coal, thus  forcing  the  gases  (carbonic  oxide)  formed  by  the  combustion  of  the  charcoal  to  pass  out 
through  the  coarse  ore  and  reduce  it  to  the  metallic  state.  The  ore  gradually  sinks  down,  and  the 
impurities  melt  into  slag,  which  is  tapped  off  every  hour.  The  operation  lasts  about  six  hours,  at 
the  end  of  which  time  the  greater  portion  of  the  ore  has  been  reduced  and  the  impurities  fluxed 
away.  The  pieces  of  reduced  iron  which  may  be  adherent  to  the  sides  are  pushed  by  the  workmen 
into' the  central  mass  of  iron.  The  blast  is  then  stopped,  and  the  mass  of  iron,  known  as  a  loop  or 
masse,  weighing  about  350  lbs.,  is  pried  out  of  the  fire  by  long  bars,  and  hammered  into  blooms  or 
billets.  Four  "operations  or  heats  are  usually  made  per  day.  The  details  of  the  process  vary  to 
some  extent  in  different  localities.  Both  the  quality  of  the  product  and  the  yield  depend  upon  the 
skill  of  the  workmen.  The  slag  is  very  rich  in  oxide  of  iron,  which  of  course  causes  a  considerable 
waste  of  ore.  According  to  Francois,"  in  the  forges  of  the  department  of  Ariege,  in  the  south  of 
France,  100  kilogrammes  of  merchant  iron  are  generally  obtained  from  212  kil.  of  ore,  with  a  con- 
sumption of  340  kil.  of  charcoal.  Richard  estimates  that  in  good  work  100  parts  by  weight  of  ore 
should  vield  31  of  bar  iron  and  41  of  slags  containing  about  30  per  cent,  of  metallic  iron.  Yields 
obtained  by  Richard  from  the  forge  du  Kessecq  were :  ore  100,  bar  iron  31.2,  slags  50.2  ;  ore  100, 
bar  iron  31,  slags  51.8.  (For  a  very  full  account  of  the  Catalan  process,  as  practised  on  the  con- 
tinent of  Europe,  and  of  the  still  more  primitive  processes  in  use  in  India,  Borneo,  and  Madagascar, 
consult  Percy's  "Metallurgy  of  Iron  and  Steel,"  London,  1864,  pp.  254-319.) 

Various  modifications  of  the  Catalan  process  have  been  made  in  certain  localities.  One  of  the 
most  important  improvements  is  the  application  of  the  waste  heat  to  heat  the  blast,  which  has 
reached  its  greatest  development  in  the  United  States.  In  1878  there  were  64  works  with  over  200 
Catalan  forges  in  the  United  States,  with  a  total  annual  capacity  of  about  65,000  net  tons  per  year. 
Of  these,  24  works  with  145  forges  were  in  the  State  of  New  York,  nearly  all  of  them  beina;  in  Clin- 
ton and  Essex  counties,  in  the  Adirondack  region.  In  1850  there  were  as  many  as  200  forges  in 
these  two  counties.  At  that  date  the  capacity  of  each  forge  was  about  1  ton  every  24  hours  ;  with 
the  better  quality  of  ores  100  lbs.  per  hour  could  be  obtained.  Using  selected  ores  containing  65  per 
cent,  metallic  iron,  2£  tons  of  ore  were  required  per  ton  of  iron  made,  and  250  bushels  of  charcoal 
were  used  per  ton.  At  the  present  date  this  practice  has  not  been  essentially  improved  upon.  The 
hearths  of  these  forges  are  about  32  in.  square  and  13  in.  deep.  The  sides  and  bottom  are  of  cast- 
iron  plates  2  or  3  in.  thick.  The  fire  is  open  at  the  front,  but  is  walled  in  at  the  sides  and  back. 
The  tuyere  is  at  the  side.  The  blast  is  heated  to  about  550^  F. ;  the  hot-blast  oven,  consisting  of  a 
few  ^-shaped  pipes,  is  placed  directly  over  the  fire.  The  ball  of  iron,  or  loop,  weighing  about  300 
lbs., Is  drawn  out  every  three  hours,  eight  heats  being  made  per  day.  It  is  shingled  under  hammers 
weighing  from  1  to  2  tons,  and  formed"into  slabs  or  billets.  The  iron  made  by  the  Catalan  process 
in  this  country  is  generally  of  the  most  excellent  quality,  and  commands  a  price  about  50  per  cent, 
greater  than  that  "of  ordinary  iron  made  by  puddling.  It  is  this  fact  which  has  enabled  the  process 
to  continue  in  existence  to  the  present  time,  notwithstanding  its  great  waste  of  material  and  want  of 
economv  of  labor. 

The  Osmund  Furnace. — Percy  describes  a  furnace  which  he  names  the  osmund  furnace,  from  the 
Swedish  word  osmund,  the  name  of  the  bloom  used  in  it.     It  is  merely  a  Catalan  furnace  extended 



upward  in  the  form  of  a  quadrangular  or  circular  shaft.  A  vertical  section  is  shown  in  Fig.  2436. 
From  a  perspective  view  given  by  Percy  it  would  appear  to  be  about  10  ft.  high.  It  was  formerly 
in  use  in  Norway,  Sweden,  and  other  parts  of  Europe,  and  "it  continues  in  use  to  this  day"  (1864), 
says  Percy,  "  in  Finland."  The  Germans  called  it  Blaseofen  and  Bauernofen,  It  is  interesting  as 
marking  a"  stage  in  the  gradual  development  of  the  blast-furnace  from  the  Catalan  forge  ;  this  and  the 
Stiickofen,  hereafter  described,  being  the  intermediate  furnaces  between  the  Catalan  forge  and  the 
blast-furnace.     The  method  of  operation  of  the  osmund  furnace  is  nearly  the  same  as  that  of  the 

Catalan  forge.      The   following  remarks  con- 
2436  cerning  it  are  taken  from  Percy  :  "  Not  more 

than  H  ton  could  be  made  weekly  in  one  of 
these  furnaces  ;  and  in  working  up  the  osmund 
or  bloom  there  was  a  loss  of  from  33  to  50  per 
cent.  It  is  especially  worthy  of  remark  that, 
notwithstanding  the  presence  of  a  large  amount 
of  phosphorus  in  the  ore  employed,  the  osmund 
furnace  yielded  good  malleable  iron ;  whereas 
the  iron  obtained  from  such  ores  by  the  usual 
method  of  producing  cast  iron  in  the  first  in- 
stance, and  subsequently  converting  it  into  mal- 
leable iron,  is  cold-shon  and  bad.  It  has  been 
previously  stated  that  the  osmund  furnace  is 
still  in  operation  in  Finland ;  but  a  still  more 
interesting  circumstance  is,  that  it  maintains  its 
ground  side  by  side  with  a  modern  blast-fur- 
nace. The  ore  treated  is  so-called  lake  ore ;  and  it  is  only  by  means  of  the  osmund  furnace  that 
good  iron  can  be  made  from  this  ore,  the  reason,  no  doubt,  being  that  the  phosphorus  in  the  ore  does 
not  pass  into  the  iron,  but  remains  in  the  slag." 

Tlu  Stiickofen. — The  Stiickofen,  Wolfofen  (from  Stuck,  Wolf,  names  for  the  bloom),  or  high  bloom- 
ary furnace  is  the  final  development  of  the  old  furnaces  in  which  wrought  iron  was  produced  direct 
from  the  ore.  In  it,  indeed,  by  increasing  its  height  and  the  pressure  of  the  blast,  cast  iron  was 
first  made,  it  is  believed  by  accident ;  and  this  cast  iron  was  then  a  waste  product,  as  the  art  of 
making  iron  castings  was  at  that  time  unknown.  The  Stiickofen  is  now  nearly  abandoned  in  Europe, 
a  few  only  said  to  he  -till  in  existence  in  Hungary;  but  a  similar  furnace  is  in  use  in  Japan.  (For 
description  of  the  latter,  see  Journal  of  (he  Iron  and  Steel  Institute,  ls-76,  No.  2,  p.  612.)  According 
to  Karsten,  the  European  furnaces  varied  in  height  from  10  to  16  ft.  In  some  the  shaft  increased 
regularly  from  top  to  bottom,  but  in  most  it  bellied  out  in  the  middle ;  it  was  either  round  or  quad- 
rangular in  horizontal  section.  One  described  by  Percy  had  an  interior  form  of  two  truncated  cones 
with  their  broad  ends  or  bases  in  contact.  It  was  16  ft.  high;  the  diameter  at  the  bottom  was  2£ 
ft.,  at  the  top  or  mouth  \\  ft.,  and  at  the  widest  part,  which  was  exactly  in  the  middle,  4  ft.  2  in. 
The  furnace  was  carried  up  a  few  feet  higher  than  the  mouth,  gradually  widening,  for  the  sake  of 
convenience  in  charging.  There  was  one  tuyere,  placed  11  imabove  the  bottom,  but  in  the  course  of 
long  working  the  bottom  or  hearth  stone  became  so  much  corroded  away  that  it  was  20  in.  above  the 
bottom.  The  operation  of  the  Stiickofen  did  not  differ  greatly  from  that  of  the  Catalan  forge.  A 
lump  of  from  1  to  6  ewt.  required  for  its  production  from  216  to  234  cubic  feet  of  charcoal.  On  an 
average  three  such  lumps  were  made  in  a  day.  The  metal  forming  the  lump  produced  in  the  Stiicko- 
fen was  described  !>y  Quantz  ( 1799)  as  soft,  tough,  and  malleable,  though  less  so  than  bar  iron;  he 
considered  it  as  intermediate  between  cast  and  bar  iron,  yet  nearly  approaching  the  latter. 

The  Stiickofen  was  at  one  time  employed  for  the  production  of  both  wrought  and  cast  iron,  the 
conditions  necessary  for  the  formation  of  the  latter  being  prolonged  contact  of  the  reduced  metal 
with  carbon  at  a  high  temperature;  and  this  is  secured  by  increasing  the  proportion  of  charcoal  rel- 
atively to  the  iron-producing  materials.  When  the  Stiickofen  produced  cast  iron,  it  became  known 
as  the  Blauofen ;  and  it  was  the  development  of  this  by  increasing  its  dimensions,  the  pressure  of 
the  blast,  and  the  temperature  of  the  hearth,  which  gradually  led  to  the  blast-furnace  of  the  present 
day,  in  which  cast  iron  exclusively  is  produced.     (See  Furnace,  Blast.) 

Modern  Direct  Processes. — Soon  after  the  introduction  of  the  blast-furnace,  malleable  or  wrought 
iron  began  to  be  made  from  cast  iron,  by  various  methods  hereafter  described.  These  constituted 
the  indirect  processes,  which  on  account  of  their  greater  economy  have  nearly  superseded  the  direct 
processes.  It  has  been  found  in  practice  that  to  convert  the  ore  into  cast  iron,  and  then  to  convert 
the  cast  iron  into  wrought  iron,  required  a  smaller  expenditure  per  ton  of  product  than  to  make  the 
wrought  iron  from  the"  ore  in  one  operation.  The  manifest  theoretical  advantages  of  direct  pro- 
cesses, however,  have  for  many  years,  and  especially  during  the  last  half  century,  led  inventors  to 
devise  methods  by  which  the  direct  processes  could  be  so  improved  as  to  become  more  economical 
than  the  indirect.  Frequently  these  new  direct  processes  have  seemed  almost  to  attain  commercial 
success,  but  the  improvements  in  the  indirect  processes  have  been  so  rapid  that  the  latter  have  more 
than  held  their  ground  against  the  former.  The  new  direct  processes  are  still  being  experimented 
upon  by  some  of  the  most  eminent  metallurgists ;  and  although  they  have  not  come  into  general  use 
at  the  present  time,  it  is  not  improbable  that  they  may  do  so  before  many  years  have  elapsed.  A 
brief  statement  of  several  of  the  modern  direct  processes  will  therefore  be  of  interest. 

Chenofs  Process. — M.  Adrien  Chenot  of  Clichy,  France,  in  1823  made  his  first  trials  of  a  process 
for  making  steel  direct  from  the  ore,  and  for  thirty  years  experimented  and  improved  upon  these 
processes.  From  1852  to  1857  several  works  were  erected  in  France,  Spain,  and  Belgium  for  the 
manufacture  of  steel  upon  a  commercial  scale  by  his  methods.  In  1871  the  process  was  still  in  use 
at  Clichy,  near  Paris,  where  it  had  been  established  in  1855,  and  near  Bilbao  in  Spain,  where  it  had 


been  established  in  1852.     The  following  is  condensed  from  Grateau's  account  of  the  process  as  con- 
ducted at  Hautmont,  in  France,  in  1857,  as  given  by  Percy: 

The  ore  sufficiently  pure,  if  in  mass,  is  broken  into  lumps  of  about  30  cubic  centimetres  (1.779 
inch) ;  but  if  pulverulent,  it  is  agglutinated  by  compression,  with  the  addition  in  some  cases  of  re- 
ducing matters— for  example,  3  per  cent,  of  resin.  It  is  then  mixed  with  more  wood  charcoal  than 
suffices  to  remove  the  whole  of  the  oxygen  from  the  ore.  In  practice  an  ore  containing  55  per  cent, 
of  iron  is  mixed  with  1J  to  U  time  its  bulk  of  charcoal.  With  this  mixture  the  reduction  furnace 
is  charged.  The  furnace  consists  of  two  rectangular  vertical  chambers  or  retorts,  about  6  ft.  long, 
It  ft.  wide,  and  28  ft.  high,  inclosed  in  a  cubical  pedestal  of  masonwork  surmounted  by  a  truncated 
cone.  Beneath  the  retorts  are  the  fireplaces,  and  below  the  level  of  the  ground  at  the  bottom  of  the 
fireplaces  is  a  pit  to  receive  the  apparatus  for  discharging.  Around  each  of  the  retorts  is  a  series  of 
vertical  flues,  communicating  below  with  the  fireplaces,  and  above  with  a  large  flue  opening  into  the 
air.  If  the  reduced  iron  were  withdrawn  while  hot,  or  even  warm,  it  would  on  coming  in  contact 
with  the  air  take  fire  and  be  again  oxidized.  In  order  to  prevent  this,  at  the  bottom  of  the  retorts 
is  fixed  a  rectangular  case  of  sheet  iron,  about  15  ft.  in  length,  termed  the  refroidissoir  or  cooler. 
The  cooler  may  when  necessary  be  surrounded  with  a  second  case,  through  which  circulates  a  current 
of  cold  water.  In  a  furnace  at  Hautmont  with  a  single  retort,  4  ft.  11  in.  long  by  1  ft.  8  in.  broad, 
the  charge  was  about  \\  ton  of  calcined  iron  ore  and  half  a  ton  of  wood  charcoal.  Reduction  is 
completed  in  3  days,  when  the  charge  is  withdrawn,  and  the  freshly-formed  iron  sponge  (the  name 
given  to  the  reduced  metal)  falls  into  the  cooler,  where  it  remains  3  days ;  and  so  the  operation  is 
repeated,  the  entire  process,  including  reduction  and  cooling,  lasting  6  days.  The  yield  is  about 
12  cwt.  of  sponge,  and  the  fuel  consumption  about  1  ton  6  cwt.  of  charcoal.  When  perfectly  re- 
duced, iron  sponge  has  a  bright  gray  color,  is  soft,  and  can  be  easily  cut  with  a  knife  into  thin  slices. 
It  may  be  ignited  by  a  match,  when  it  continues  to  burn  until  wholly  oxidized.  The  imperfectly 
reduced  ore°has  a  black  color,  and  can  neither  be  cut  nor  ignited.  A  modification  of  Chenot's  pro- 
cess consists  in  reducing  the  ore  by  a  current  of  hot  carbonic  oxide,  and  not  by  intermixture  with 
solid  carbonaceous  matter.  The  reduction  chamber  is  connected  with  two  carbonic-oxide  generators 
on  each  long  side,  communicating  with  the  reducing  chamber  near  the  bottom  and  above  the  top  of 
the  cooler.  After  the  sponge  is  removed  from  the  cooler  it  is  balled  together  in  a  charcoal  hearth, 
and  hammered  into  a  bloom. 

A  report  on  Chenot's  process  made  in  1856  by  MM.  Combes,  Regnault,  and  Thiria  to  the  French 
Minister  of  Public  Works,  says :  "  It  is  not  probable  that  these  processes,  in  their  actual  state,  could 
be  applied  with  advantage  to  the  manufacture  of  iron,  except  perhaps  where  rich  ores  of  iron  might 
be  procured  at  a  low  price  and  labor  would  be  cheap."  The  French  Exposition  of  1855  granted  the 
medal  of  honor  to  M.  Chenot,  considering  his  process  the  most  important  metallurgical  improvement 
of  the  time. 

Clay's  Process.— In  1837  and  1840  Mr.  William  Neale  Clay  obtained  two  patents  in  England  on 
a  process  for  making  wrought  iron  direct  from  the  ore.  In  this  process  the  purer  kinds  of  ore  were 
crushed  to  lumps  not  larger  than  a  walnut,  and  these,  mixed  with  one-fifth  their  weight  of  charcoal, 
coke,  coal-slack,  or  other  carbonaceous  matter,  were  subjected  to  a  bright-red  heat,  in  a  clay  retort  or 
other  suitable  vessel,  until  the  ore  was  reduced  to  the  metallic  state.  When  the  reduction  was  com- 
plete, the  spongy  iron  was  transferred  direct  to  a  puddling  furnace,  where  it  was  balled,  and  then 
wrought  into  blooms  under  a  tilt-hammer.  The  process  succeeded  in  making  an  excellent  quality  of 
iron,  which  however  was  not  uniform,  but  it  was  commercially  a  failure. 

A  modification  of  Clay's  process  was  tried  at  Workington,  England,  which  was  not  abandoned  till 
after  1,000  tons  of  bar  iron  had  been  made  by  it  at  a  heavy  loss.  In  this  modification  the  ore  was 
reduced  directly  in  a  puddling  furnace.  A  mixture  of  ground  hematite  with  about  one-third  its 
weight  of  coal-slack,  washed  in  a  solution  of  soda  ash  or  brine,  was  used,  and  smelted  in  conjunction 
with  pig  iron.  To  the  mixture  of  hematite  and  slack  there  were  added  about  4  lbs.  of  fire-clay,  4  oz. 
of  soda  ash,  and  6  oz.  of  common  salt  to  each  112  lbs.  of  ore.  The  bar  iron  produced  was  tolerably 
uniform  and  of  fair  quality. 

Renion's  Process. — This  process  was  patented  in  the  United  States  by  James  Ronton  in  1851.  It 
was  carried  on  upon  a  commercial  scale  in  Cincinnati  and  in  Newark,  N.  J. ;  but  it  proved  a  failure 
in  economy,  although  good  iron  was  produced  by  it.  The  furnace  in  shape  resembled  an  ordinary 
puddling  furnace,  having  a  fire-brick  chamber  at  the  end,  10  ft.  high,  6  ft.  broad,  and  7  in.  wide. 
This  chamber,  which  was  in  fact  a  large  vertical  muffle  or  retort,  was  entirely  surrounded  externally 
by  the  flue  or  chimney  of  the  furnace.  It  was  filled  with  12  cwt.  of  a  carefully  made  mixture  of 
from  20  to  25  per  cent,  of  ore,  and  from  75  to  80  per  cent,  of  coal,  both  finely  broken,  and  became 
sufficiently  heated  to  cause  the  reduction  of  the  ore.  The  reduced  ore  was  dis